New tranny or simple fix? Help!!!

[Cooper-97gst]

Hi i just picked up a 97 gst spyder from a friend for $500 after negotiating $6000 off an 08 350z for him. Not bad eh? Well i had the car for about one month and had the transmission(auto) give out on it ( at least i think it did) i didnt put one hundred miles on the car in the month iether. as i was driving it one day at about 35mph the tranny down shifted to firts gear on its own. it wouldnt move after that. i checked the oil level and it was low about a qrt, but it smelled burnt. after allowing it to cool down and adding atf i was able to get the car home but the tranny would hold the gears often 1st, 2nd, and 3rd . it also makes a winning noise when its off park. he bought the car in 03 and it had about 90,000 miles on it . the car has 135,000 now. he used the car to go to work 10 miles out threw surface streets, so the car hasnt been raced or miss treated in that sence. however, knowing my friend im sure he never had the tranny serviced. i went down to my local transmission mech and gave hime the same story, he said he could rebuilt it for $1200. i had another guy come look at the car and said if i take it to his shop he could get me a used one for $450 and swap it $250. im wondering if a simple oil and filter change will do the trick or if these guy are right and i need a new one. also if anyone knows of any up grades i can do (more bang for my buck kinda thing) to get my friend back for this. i wanna spank him with his old car and him in his new car i have an injen cold air intake, hks blow off valve and a hks exaust with 3'' pipe other than that its all stock...thanks in advance for all your advice.

 

[DSM_IKE]

I would say no not a simple oil and filter swap. Tranny sounds toast to me.

 

[92AWDHX40]

Looks like you need another tranny i will never buy a used one too many issues, new trans built for me, the added insurance i need.