Things to look for:
I was looking at all the pictures, and the picture of the engine bay I see the oil stick is missing? And I am wondering why there is oil all around the filler cap. I would check all fluids for instance, radiator should be clean & green and no rusted water in the mix and at proper level. And check the overflow bottle also it should be green. Transmission, should shift 4 times + overdrive. Tranny should be check in N running,after the engine & tranny is at normal operational temp. Be sure you check both side of the stick and always fill on the low side. Now the fluid should be nice and red and no burnt smell. Check to see if it has a lift pump by the starter or has been upgraded to in tank module. Be sure to check out the 4X4 hi and low. Also do a history search vin # to see how many owner, accidents, maintence what was install. I hope I didn't scare you. These engines are built to last..