You should get lots of responses and if you search, there are other similar threads. I have 3 of these 5.0 AWDs so I like them. You might ask why it has been painted... maybe it has been in a wreck, you can see the V8 emblems are missing and it does not look like the factory paint. If it has been in a wreck, check out the areas that were damaged closely. You might want to do vehicle history check. Also, with those tires, you will be lucky to get 15 mpg anywhere. I would ask him to take them off and discount the price for new tires. I would ask him what he knows is wrong with it and what maintenance he has had done.
If it has gone to the dealer, it should have relatively new shocks, relatively new ball joints, throttle body cleaned recently, and all fluids should look good. Brake fluid should not be green, oil should not be black, trans fluid should not be dark and smelled burned, coolant should not be rusty colored and should be antifreeze and not just water. Power steering fluid should not smell burned. As far as reliability, I would go through and make sure everything is working on it, piece by piece. While in general I think this is a reliable vehicle, it depends on what you say is reliable. I like these because I can fix everything on them and I spend some time each month on one thing or another to keep them running and operating perfectly. The motor and transmission are relatively reliable, but they do wear. For the engine, you could do a vacuum check and compression test and look at the plugs. Otherwise, you can drive it and make sure it is not burning oil ( you can look for blue smoke on start up) and it check to see if it hesitates or misses when driving. Try slowly accelerating on a long uphill slope, the miss might be easier to detect this way. Listen for a ticking noise, could be a valve or exhaust leak. I would get under the vehicle and look for leaks. Rear main seal is likely leaking some, check oil pan for leaking, check transmission pan and hoses for leaking, check coolant hoses and radiator for leaking, check power steering hoses for leaking. The transmission can develop a "shudder" where is goes in and out of OD so when you drive it, try to get it at exactly the speed where it shifts to see if it shifts smoothly. Repeat a few times. Once the trans is warm, cycle it through from P to R to D and back and stop at each one. It should shift within a second or two. Repeat a few times. Check to see if the front drive shaft has been removed, if so, likely have a transfer case problem. Check all the lights and gauges, turn signals, brake lights, interior lights, dash lights, fog lights, head lights. Make sure all the warning lights come on when you turn on the ignition, including the check engine light. Check the door locks, wipers, rear wiper, defrost, power windows, power seats... Check all the door locks, door ajar lights, door chimes, check the rear hatch to open and close and latch and unlatch smoothly, check the struts on the rear window to be sure they hold it up. Check brake pad wear and make sure it brakes smoothly and evenly. Check to see if the master cylinder is leaking by seeing if there is brake fluid at the brake booster housing to master cylinder connection. Check to be sure the parking brakes work and hold with car in drive. Check the A/C and heat and make sure all of the temps, fan speeds and all the vent selections work as they should. Listen to the A/C compressor when it is engaged and make sure it is not making a loud rattle. Since he has installed an aftermarket stereo, make sure the door panels are not loose and he has not damaged the door panels or dash. The center console is worn/torn and that is common, you can get a repair cover for it. My guess is as you are going through these things, he will start to tell you other things that are wrong with it. My list is incomplete. I think with those miles you can expect you will have some issues pop up over time, so it depends on what you are willing to live with or fix.
