Sadly i went through this same thing with my 2.4L highlander a while back. The car was fine and then suddenly it lost all drive (no power being transmitted to the wheels). I managed to limp her to toyota (cold tranny) to find that the entire gearbox was shot and little metal pieces had been tearing up everything inside the gearbox.
The ATF was changed a few days before but the idiot mechanic didn't tighten the bolt and the fluid level dropped dangerously low. as my dad was sick back then i didn't pay attention to the fault thinking that i'd do it soon (which i didn't and the car stayed in daily use. The highlander uses all camry running gear but it has button shifters on the steering wheel and if i wanted it to work i wasn't able to use a camry part. I ended up biting the bullet and spending 7 lacks for a new gearbox (this is the price after discount). I've not had a problem since.
I'd suggest he gets a factory part from the dealer, fixes the car and sticks with it then as it'll be 100% fine after that. no point dumping a perfectly good car.
