Well, I guess I'd start by asking the following:
- What's your budget?
- What's the extent of your mechanical abilities?
- What's your timeline?
Assuming that your car isn't eat up with rust, it can be restored. Yes, it will be expensive, but you certainly don't have to do a complete frame-off restoration. The big ticket items will be the usual suspects (engine, transmission, suspension tires, etc.), like on any other car. Parts for these cars are relatively cheap and easy to find. I owned a 60's Mercedes a few years back that's upkeep would make a multi-millionaire wince! Maintaining these Buicks is quite cheap, compared to many other classic cars.
At the end of the day, it really comes down to you and what you want. If this is the car that you want to save, then I say have at it. You can always stop working when funds run dry and pick it up again later. That's what I've been doing on my project. If you read through my thread, you'll see that I was very ambitious about the timeline in the beginning. That was 2014 and the cab still isn't back on the frame. 🙃
Value is tough to peg because some buyers see treasure where others see a pile of junk. As an example, I paid $4,200 for my 1951 in 2014. It ran, but not well. It didn't drive because the brakes weren't working. Fuel was leaking everywhere from a busted line. The car had a nice newer (early 90s?) interior but was otherwise original. The floor pans were rusted out. The tires were junk. I still saw a $4,000 car. I knew that I was going to be tearing it down, so I wasn't concerned about those little things. If I had been looking for a good driver, I wouldn't have bought this particular car; I would have paid ~twice as much for one in better shape.
When it comes to these Buicks, it's a buyer's market. The only way you'll know the value is to list the car and see if anyone bites. I'd start at $1,200 and work my way down. The car is worth more as parts than it is whole. I'd give you $100 for a decent 51' hood ornament right now! 😛
My $0.02: Bringing any car back from this point is a labor of love. If you're not in love with this car, it's probably best to let it go.