Was running some errands the other day and the.

Was running some errands the other day and the car started shifing funny, taking high RPM's to shift, and stalling at a light. It started right back up and for the next couple lights I had to feather the peddle to keep it running. The shifting then seemed to be fine. At the last light it died as I was making a left hand turn. I coasted to the shoulder and it started back up. Went 1/4 mile to my destination, parked, was inside for 5 minutes then came back out to get it home. It started in the lot, still would not idle, and as I went from reverse to forward it made a screeching noise and died. Hasn't started since. I checked the timing belt and it is in tact. Local parts guy thought it may be a computer problem. One other thing. Recently had my oil changed and when I checked the level it is reading that it is overfilled by quite a bit on the dipstick. Any ideas?