looking to buy a Cherokee

I have been looking around and have found that the Jeep Cherokee is what I
am looking for, 4x4 suv, inline 6 engine and not too big. A few questions
though.

what kind of gas mileage would a Cherokee get? (4x4, I-6, auto/manual
trans)I know it wont be an economy car, just want to make sure its better
than 11mpg (with my current truck)

How many miles do they go? I am looking in the $5000 and under range, and
they are mostly over 100,000 miles. and as many as 330,000 miles. What parts
need to be replaced or looked at around 100k?

what are the common problems with them? how much does it cost to own such a
rig? I plan on keeping it stock and mainly driving it to work on the
freeway, and spending the weekends off the pavement.

what years are better than others?

what was the first year for fuel injection?

any input would be very much appreciated.