Welcome to the sty. i agree 100% with J Mack. i dont want to dissuade you from a pig at all. however if you want something that is less hassle, cheaper to fix and less frustrating overall but still pretty cool consider a 40. but if you already have a jeep you kinda already have a 40

, if you feel up for the challenge and want something truly unique. get a 55.
all that being said i have just a few recommendations. i have a 75 and this is what i wish i knew going in.
55s are rust magnets so the less rust a pig has the better. while not impossible body parts are really hard to come by. bob M makes some really nice metal pieces that replaces many of the trouble areas but some places that get rust are a real pain to fix. welding while not 100% necessary will definitely be a useful skill. i too learned to weld just so i could work on my pig.
Find a pig that runs. even if your ultimate plan is to do an engine swap its nice to be able to take it out and put around town in a vehicle that most people have never seen.
Get a pig that has all of its glass in tact. once again glass is hard to find.
Plan on going 4 wheel disc brakes to me i cant imagine mine any other way.
For me power steering is a must. i had mine for a year without it and i cant imagine it any other way.
Get a 4 speed. i know some people may totally disagree with me on this but I almost bought a 3 speed and am so grateful that i didn't.
if i had to nail down just one trouble item with the 55 it would be the rear window. more likely than not you'll have some problem with yours. the main thing that breaks is this little plastic gear the good news is they make a plastic replacement as well and a very sweet brass one. but if your rear window already works when you test it its a plus.
if you find a pig with original mirrors that are in great shape put them up on ebay and you'll be able to fund a good portion of your pig. (half kidding and half not)
as far as learning to weld i have just a few unsolicited suggestions.
get a decent welder don't skimp too much on it. this is one tool that definitely quality counts. i think miller or Lincoln are the only way to go here. I have a Lincoln and i love it.
dual voltage isnt necessary for most body work but it is sure nice when you need it.
get a gas mig welder dont mess with flux core if you can avoid it.
there are two guys on youtube that i learned a lot from, jody @ weldingtipsandtricks and chuckE2009. there is hours of good material there.
you know how they say that when all you have a hammer everything looks like a nail. once you get a welder you start looking at metal in much the same way. welding is a heck of alot of fun.
at any rate thats just my 2 cents.
i hope it is helpfull