...I am not sure where to start...
First, I personally am not a fan of Prestige or Josh Towbin. Just a personal thing. That shop has a tendency of...well...they dont call them Stealerships for nothing. I ended up picking up my JKU at Centennial for a steal. So I highly recommend you shop around. Mine was way way way below blue book and runs like a top, but I also do my own work on it.
Second, I suggest you test drive a 2012 or newer. It might be a tad more than you would want to spend (possibly) but they do have a LOT more power.
Three, if it is a hardtop make sure when you test drive there is no whistling. If there is have them pressure wash it and hit the top drivers side while you are in it. Make sure there are no leaks, some do and while it isn't a "hard" fix it is something to fix none the less.
Check the under body, see how the skids are. If they are scratched and dented to hell you know it was wheeled and possibly hard so you would have to check for other things, such as a bend front axle. Check to see if there are any mods on it. If it was owned by another forum member(any jeep forum for the most part) there will be some mods. Such as side marker lights flashing when you hit the turn signal. Look in the glove box, mine had the original build sheet and owner name. I am the third owner and that sheet helped answer a few questions. Mine was fully stock when I got it, lol.
One thing I always do when testing a used vehicle is drive it very slow in a lot with windows down, listening for any clicking [signs of locker or possible problem(s)], look for fluid leaks and the part I sometimes enjoy more than anything, shaking the heck out of it to test the shocks and watch the salesman's face.
If it stops rocking after a few rocks shocks are good. If it keeps going past 2 or 3 they will need to be replaced soon. It also allows you to listen for any binding or metal on metal contact, not always possible but can be.
Hope that helps a little. Lastly, do your research. Last time I was on that lot I had multiple salesmen try and sell me a JKU that had numerous issues and was way over priced. I pointed them all out and they tried to do the old smoke and mirrors and tell me it was supposed to make those noises. LOL. Each experience is different there though and in general all dealers suck...some more so than others.
Perhaps check out Chapman and Sahara too. Chapman has Jeepers that work there and speak our talk and Sahara I hear good things about plus the service manager is a or was a Jeeper.