I wouldn't lift it. You'll be able to fit 33" tires with the factory lift.
If you can find a driver side battery tray from a civilian diesel model, you'll have a great start to a dual battery system.
Make sure you pull off the front brake rotors and grease the wheel bearings - one of mine locked up and it was a pain to get it off. Don't flush the transmission.
If you want to do a fluid swap, that's probably fine, but do it using the instructions
here.
If your steering is kind of loose, check the ball joints, tie rods, and drag link for play. If they are all solid, check the steering box bolts and the frame where it attaches - this body style is known for issues in that area.
Finally, go and browse CK5.com. It is one of the best resources on the net for the old square bodies.
edited to add: holy crap, I just saw it caught fire. my condolences.