alright I dunno about the other guys but a little rule or advice from me: Don't fix it if it's not broken. If your brake lines break then you can replace them with whatever you want.
I don't think you're a dealing with traditional bumpsteer, if you open your hood (or just look the grill) you can see the little steering box, to the right of the radiator while facing the car. On top of that there are a few pieces including a nut with a philips head. Take this with a grain of salt, or advice from one of the more experienced guys but I'd bet you'd fix your problems by adjusting that correctly.
Which for me meant unscrewing the nut then tightening the screw until snug then un-tightening like 3/4 of a turn.
As for the brakes, I like the idea of all wheel discs too even stock, I think it just looks better.
But if you don't and you're actually doing it for practicality you really don't need it, just change all the pads and possibly the rotors.
I'm assuming you mean Anti-Lock Braking System by ABS. In which case I'd probly just forget about that, my 96 subaru had the original anti-lock and it sucked. Not to mention adding one would be Difficult and Not budget.
You'd have to find a way to ad the little extra discs that get attacked. Not to mention the computer that knows when to attack them so you don't just randomly stop everywhere you go.
I'll try backing up in 4hi in a little bit, but I don't really think you should be concerned.. maybe reverse doesn't go through the front output and it binds the axles a tad. No idea, ask the other guys if you must but I wouldn't be worried.
I think you're talking about the petroworks transfer bushing set, I'm putting my money on that. your u joints could probly using greasing or replacing but I would guess they'd have more consistent problems.
A harbor freight winch that would actually do any better then a hand winch for a Stock samurai would be somewhere around 250-400$ a hand winch being under a hundred. Not to mention you'll probly never get stuck enough to use it, but a hand winch will do what you need in an emergency.
Oh and I think you'll find most of us don't have a/c, it was a rare option and More rarely still Works. But a heater might be possible and definitely a radio.

Hope that helps a little??
Guys lemme know if I screwed up or gave mis info, kinda new at the whole advice thing.. thought I'd try it..