My opinion is to get it working right, keep it, find a good way to store it if you can (do you have a garage?), and drive it.
Even if you change your mind later, you'll get more money for it after it's cleaned up and working, than you would by just selling it as is.
Reasons to keep:
1: It was your father's car. I tend to save/use many family items; I even bought my grandfather's house, and lots of small random tools from family. I think it would be nice to keep something of your father's around.
2: It's a very nice, comfortable car regardless. I'm not sure what kind of car you have now, and what you've heard about big American cars, but these cars are not nearly as hard to park or as bad on gas as people would have you believe. You'll probably get about the same fuel mileage as a medium sized SUV, but with far more comfort.
3: Even though I'm sure your father's car is beautiful, to be honest, it isn't worth all that much to sell it, at least in my opinion. The Town Car ran with nearly the same styling up until 2011, but with constant mechanical improvements. If someone wanted a really really nice Town Car and they had some money to spend, they would probably just buy a low-mile 2010 or 2011. I don't mean that to insult your car, just to be practical. Your car is definitely worth money, just not BIG money. That would make me rather keep it than sell it.
What I think you should do, whether you keep or sell:
1: Check all fluid levels before even trying to start it. (Transmission fluid is supposed to be checked with the car running, so you can't accurately check it with the car off. But just pull out the dipstick and make sure you have SOME fluid on it.)
2: If no one told you yet, you'll need a new battery. You might get lucky and be able to charge it and/or jump start the car, but it won't be reliable long-term. So just budget $75-100 for a new battery.
3: Get the oil changed as soon as possible. The transmission fluid and coolant could wait until you get the car up and on the road, but I wouldn't take a chance on the old oil. If you're a do-it-yourselfer, you might want to consider even changing the oil right there in the garage before you start it. (However, changing the oil with the car cold, you won't get all of the old oil out anyway. So you could change it once in the garage, drive it a couple hundred miles, then change it again with the car warmed up to be extra safe. It's cheap insurance.)
Personally, I would just make sure the oil level is full, then go ahead and start it up; the old oil should be good enough for the car to run for a few minutes and move it around. But that's just my opinion, and you may be more risk-averse than me. If you're really really worried, you could consider even having it towed to a mechanic and let them change the oil before starting it, but that'll cost you.
Regardless, when you first start it, expect a knocking noise for a few seconds as the oil travels around the internals of the engine to where it's supposed to go. But then if it doesn't start to run smoothly after 10 seconds or so, shut it off and figure out why before anything gets damaged.
4: I wouldn't scrub all that dust and dirt off with sponges or brushes. I'd try to get the majority of it off with careful use of a pressure washer before giving the car a regular wash, so the dirt won't scratch the paint as you scrub the car. You could use a pressure washer at home, or drive it to a coin-op car wash where they even have a pressure washer that sprays soap under pressure.
If you can't do that, at the bare minimum, remove as much dust as you can by just rinsing it with a garden hose, before any rubbing.
5: You're going to need to replace some parts from sitting, but I don't think you'll really know what parts they are until you get the car up and running and moving. I wouldn't go crazy spending all kinds of money replacing every random thing at first. Just do the battery and oil, get it running, let it idle in the driveway for a little while (without leaving the car unattended). If something starts to leak or make noise, figure out what it is.
6: It would be no surprise if it needs tires by now, but I'd suspect the original tires would be good enough to hold air and move the car around. Don't forget to put air in the spare tire and then check it in a week to make sure it's still holding air.
7: The brakes are certainly going to make grinding sounds and squeaks as you move the car around. Don't get scared----it's probably just surface rust on the rotors. (Rotors are the disks you can see looking through the wheels. If you look at any regularly-driven car they'll be shiny. Park the car for even a few days and they get a little rusty.) After you drive the car around a little bit, you'll see whether the brakes will clean up and work OK, or need some parts replaced. Just drive around the block and make a few stops, and they'll pretty much scrape themselves clean if they can.
8: After you get it running and moving you (or your mechanic) can make some decisions about replacing things like the serpentine belt, some/all radiator hoses, brake hoses, and things like that.
9: Don't be surprised if the air conditioner has slowly leaked out its refrigerant and doesn't work. Should be something like $100-200 to vacuum and recharge the system, and at that point you can see if it works, and if it has any major leaks or not.
All in all.......I'd figure on $1000 for battery, tires, and replacing all fluids. Could hit $2000 if you want/need to start replacing hoses, belts, and brakes.
By the way, I'm not sure if you're handy with cars or not, but if you want to learn, this is the right car. They're straightforward to work on, there's lots of information available, and parts are cheap. Go to autozone.com and look up prices on things like brake rotors, belts, and so forth. You could save LOTS of money doing some or all of these things yourself.
I hope I didn't say too much or too little.........but seriously, it's worth more up and running than sitting there dead and dirty. So get it going no matter what; it won't cost much to do the very basics like the oil change, battery, and a quick wash. At that point, drive it a little and see if you like it, and see what else it needs and what it will cost. You will get a better price, and more-interested buyers if the car looks good and the buyer can at least hear it run and move it up and down the driveway.
Also, another strategy might be to get it fixed up, put it for sale at a way-too-high price, and see what happens. If it sells, you get some good money. If no one wants to pay, keep it and drive it.
And sorry to hear about your father.
