Everybody has some good advice, as an old car lover (and a person who has restored a couple of cars, and have alot more to restore) here is mine:
59 chevy is worth it, take a look here
http://www.manheimgold.com/ for a rough Idea ( don't think you have a gold mine after reading that).
the Engine swap will be pretty simple, it will require some motor mount adapters which are relatively cheap (older Chevy small blocks mounted father back on the engine then the newer ones). Also if it has a late model automatic tranny, that would be worth swapping also. Somebody mentioned the fact that older engines wont last long on the fuel we use today (do to lack of lead content). Depending on budget and such the motor form the monty should be an Ok choice, ok milage and should last .
bodywork, simple to do , hard to do correctly. It is hard work, but the finished product and the fact that "you" did it can make it all worth while. Bodywork can be the cheapest part f the restoration if you do it yourself (again cheap is probably not the correct term as sandpaper, tools, and time all do add up). Its what I went to school for, I love to do it, so it doesn't seem like work to me, but I know others would (and did) say it was hard work, it is. But it can be fun too if you enjoy making something out of nothing. The biggest things to look at is quite simply RUST, not in the visible spots, but in spots you don't look for, under the carpet, int he seems of the trunk, jack it up and look behind the door sills, lower part of the fenders (behind and in front of the wheels). Is the chrome all there? Most stainless chrome (all the side chrome on those cars) can be shined up with a kit you can buy and use on a bench grinder, again it will take time (and I would recommend some junk practice pieces) but the cost wont overwhelm you if you do it yourself.
Interior: This may be the easiest or toughest, depending on your budget. Another thing that is really easy to do, hard to do correctly. I liked the little time we where taught upholstery in school (its required to take a general in it when you do Auto Body) that I went to school for it also and did it for 10 years as my only job. Doing this yourself isn't easy as it requires a heavy duty machine (not your moms or wives).. some home machines can do the work required, they just wont stick close enough for most jobs. Most interior stuff is available to purchase, but a complete interior could cost easily $2000+ for all of it.
After all that, you think you have something... well you really don't.. You will most likely need to rebuild the suspension, and if you really want to DRIVE the car, I would re comend late model brakes (again, not horrible as there are kits and such to make it fairly easy). Rebuilding the undercarriage is another problem as it takes a few special tools. the parts are fairly cheap, but this is something I would not suggest to the backyard guy.
then there is stuff like Fuel lines and gas tank (probably just fine but if its been sitting?), brake lines (the steel lines are probably OK, but the rubber (one on each wheel) will need replacing), electrical wiring, have mice been in the car? How do the windows and door locks work? The heater system, are any of the controls broke?... most of this last stuff is frailly easy to fix, but it all adds up.
its a project i would recomend anybody with the ambition to try, but dont think its a quick thing, and if you honestly dont have the time, it wont retore itslef.
here is a link to some of my projects, a few finished ones and alot to be finished.
http://clok1966.tripod.com/id3.htmlAll i have to say is 59 2door chevy, nice car, wish I had one.
Clok