The 2002 Tracker, as you say is bigger & heavier than your 96, it is however, pretty much the same 4WD system you're accustomed to - the only challenge I see is a "space" challenge, it does need a little more room to maneuver - so if you think you're OK with that, then go brave.
The trouble spots to be aware of ...
- the V6 uses timing chains and if routine maintenance has been missed, they can be troublesome & expensive to fix - you really want to hear the engine start from cold, if the chains rattle walk away.
- some years had insufficient corrosion protection on the front suspension cross member - get down & eyeball it.
- the front freewheel is built into the front differential - select 4H with the ignition on and watch the 4WD light on the dash - it should come on in 1~2 seconds and stay on, if it flashes, there's an air leak, the faster the flash, the bigger the leak, a wink out once every few minutes can be ignored.
Other than the above items, I think you just need to look for the stuff you'd check on ay used car - dents, rust, leaks, etc..
The bigger vehicle will burn a little more fuel, it's a lot more comfortable, partly because of the longer wheelbase - I think it's a great truck - stock tire size is about a 27", you can go to about 28.5 with no lift & no trimming, a 29 will require a small lift and possibly a mild trim of the front bumper plastic - I can't give you specifics on the tire sizes if we're discussing Trackers, because those run 15" wheels, I have a Grand Vitara with 16" wheels, and those are approximate numbers based on what I've used.