91 Jimmy rolls in park

91 Jimmy 4WD automatic 4.8 TBI

vehicle stopped running recently & was towed to garage for me. Those idiots towed it from front. They deny it but hatch of vehicle was against a wall in their lot. Had it towed (from rear) to my house because I didn't trust them to fix it after knowing they towed it wrong. Now it rolls when park is engaged. Checked the shift linkage & it is not disconnected. Brakes hold when you press them. It was suggested that the parking pawl is now broken because the idiots towed it from the front. I need ideas on what may be wrong.

Also, vehicle was back firing and running rough when I stopped to get gas. Turned it off & then it would not start back. Asked gas station to call me a tow truck. My son & I pushed it out of the way of the pumps so access was available to front & rear of it. Left it unlocked & in neutral with wheels chocked as I had a test and couldn't wait another 30 min for the tow truck.

It gets good spark and has new plugs (1 week old). Wires were changed with last set of plugs. It has stalled a few times recently. Need ideas on what to try to get it going again.