I replaced my battery yesterday at Reilly Auto parts. The guy installed a 26R72 on my 1990 Mazda 929 while my car was running. Sparks flew when he disconnected my old battery. I questioned him since I wasn't aware you could do that and not damage the electrical parts. It cranked fine, but hesitated like it wasn't getting enough juice. I went back to asked him to check if the proper battery was installed, since it was much smaller than my original battery. I asked him to let me try an upgrade thinking it had more power. This was a 35EXT, plus more money. I pulled out of their driveway with the car hesitating, barely making it to a place to park. The car would not engage in any of the gears, but the engine was running, I just couldn't get it in a gear to drive home, leaving the car in an empty parking lot. I'm picking the car up not knowing what to do. Did removing the battery cause a fuse or some other electrical part to short out?
My only problem with the car before I had the original battery replaced, it was four years old and not holding a charge. Can you please advise me on the information I gave you?