1995 Dodge Stealth Car Hesitating and CEL on after transmis

I just had a rebuilt transmission installed (2nd time in 8 years) and car ran fine on the way home (2 hour drive) except that the CEL was on. I called my mechanic and he said he didn't have the right equipment to reset the computer and the light should go off by itself, most likely by the time I got home. He also told me that he replaced the battery because it wouldn't hold a charge (he had to remove the battery to install the tranny).

The next day, however, the CEL was still on and the car has virtually no power on acceleration (forward or reverse). I couldn't even make it to the end of the street and pretty much had to coast back to my driveway. The car idles fine in park.

I've pretty much had everything replaced/repaired on this car and recent service includes air induction sensor, head gasket, plugs and fuel pump/filter.

Is there anything you can suggest that I look at and possibly fix myself before I have it towed to my mechanic and spend yet another several hundred dollars?

Thanks, Anita