firstly the r200 LSD is the standard diff....
you have to remember they are a 20+ year old car now, look for the general things first, rust in the wheel arches, window lips and the boot...
if its a 2door then check the rubber seals between the windows, major hassel to replace...
Price can very depending on year, condition, non turbo/turbo version 2/4 door, its realy what your willing to pay..
parts are a mixture of easy and very hard to get...
after market parts... engine wise not hard as you have places like www.fj20.com and datsun clubs who love the FJ.. suspension is another thing, custom or imported for coilovers $$$ or you can convert to s-13 for around 2/3s the price of imported or customs..
hope thats a help..