1988 Chevy Cavalier what to do.

At first it was just the grinding sound when I turned the engine over-took it to my mechanic and they "cleaned" it up (I can't remember the proper word he used) then it did start without the noise but immediately stalled on a slight hill when I left the mechanic. I went back and told them about the stalling and he disconnected eps? (Said sometimes when you step on the gas it sticks and that could cause stalling but disconnecting it wouldn't hurt anything). Drove it more and noticed lurching on all hills and especially around 35mph, but it hasn't stalled while driving-some times takes more than one try to start though. Took it back today but they didn't get a chance to look at it-talked to the mechanic and he suggested disconnecting overdrive. Had to take back the car tonight and will return tomorrow so he said to listen to hear if it changes gears as I drive-i wasn't hearing that before. My first car (many, many years ago) lost it's transmission about 92 days after I bought it (and the warranty expired). I put that awful episode out of my mind so I can't remember what led up to it but I'm concerned i'm headed there again.