Seems like a lot of people are talking about the mega heavy trucks.
I guess I will toss in my two cents.
I have owned a really very nice blazer, it was great, beautiful condition, and did its job very well. I really enjoyed having that vehicle. When it went the way of all the earth I had a few different cars, and now I have a WJ Jeep. WOW that thing is like cheating! It goes everywhere I want with a 2" buget boost lift ($150 installs in about two hours if you are slow) and some JKS Disconnects for the swaybar (about $100 and again installs in about an hour if you are slow). This thing is quiet inside, it drives really nice, it is extremely comfortable, the sound system is nice, oh and you can HEAR it when you are driving down the road.
I have had to do VERY little with it beyond basic preventative maintenance, and I have a very high mileage jeep.
The "major" issuses with the WJ are the headlights get foggy after a while $60.oo to replace (per) and the power windows have a plastic clip that holds the cables inside which can break easily (about $50-100 to replace and an easy job).
If you get into the mega nice ones and in the 03/04 years there is the issue of the heat blend door. Do your reading on this, if you get one of those jeeps just find one that has had the work done already because it is about a $2k job at the stealerships.
Another bonus about this jeep is that it is the newest vehicle in the price range you are looking for. That means you are going to have to do less to it than the others (in general).
I would also consider a ZJ jeep.
For Mileage the econemy goes, from worst to best...
ZJ V8 (fairly mid range mileage, not much worse than the I-6)
WJ/ZJ I-6 IO get between 12-14 city and up to 17 HWY
WJ V8 17 city and 24 HWY. These are not exaggerated either, my folks have one and it is great!
Last thing, IF You want to modify this vehicle such things are prolific, to say the least, in the industry. Also as so many people modify them, parts for stock jeeps are also rather prolific.
Good luck!