4 months left on warranty? I assume that means its new / rebuilt / swapped engine?
Like
@Flyfishjeep said, check for leaks (which your bound to have some oil somewhere with it being a 4.0) its just a matter of how bad typically. But Definitely check that radiator fluid. 2000-2001 years have known problems that you can search (google). I'd also look more into that rust. Due to their age, and how they were built/material , are rust prone and some areas can turn into a nightmare. Ive seen guys replacing entire floor pans/ and daggum nearly the whole jeep, and thats not worth it to me.
Others will certainly chime in on this forum, but Id also tell ya to check out CherokeeForum.com there is TONS of info on that site. Use the search function over there and you can find step by step details to any and all problems you'd ever come across. (believe me I've used them a lot haha).
On a personal side, I'm hesitant to buy used vehicles with lifts and thats for several reasons.
1) you dont always know what you have or its shape
2) you dont know the competency of who put it on
3) (in my experience) lifted vehicles tend to be ragged out and abused.
4) and others....
Price isn't everything. Condition and how it was maintained is important. People ask/pay more than I ever would for a rusted out beater, and then others find a diamond in the rough , beautiful garage find, and pay next to nothing.
Good Luck! and let us know what you end up doing (and pics of course!)