what do you guys think about this buy

came a cross a 2007 4runner v8 limited with the 3rd row(looking a suv with 3rd row) they are asking for $16000 but when i drove it today. there was tranny issues. drove off the lot fine but when i came to the second stop light. felt like it had problems down shifting. was jerking a bit but you'd have to pay close attention to feel it. then on the pickup. there was a slight vibration right before it start going. drove it foe several miles and then i noticed while pulling into where my wife works at. i gave it gas and it was just barely going. let off the gas pedal and back on and it was fine. long story short. on my way back i had several issues with it picking up speed after stopping at several red lights and also would jerk and jump a lot. anyways, i really like the 4runner and wouldn't mind paying to get it fixed but am not going to pay the price they want for the 4runner.

do you guys think its worth buying(if theyll take my offer) and then fixing/replacing the tranny?

how hard is it to replace a tranny on the v8 4runner if i was to do it myself