Hey everyone. new to forum. Hoping for some much needed help.

Own 1996 buick century, 3.1. Had to local shop for a diagnosed blown engine. Picked up after coughing up almost 2 grand. 2nd day, vehicle idle was up and down badly, brakes when stopping would let loose almost to floor and low traction,antilock light would come on. Also made real loud grinding noise in dash area. If that is not enough, vehicle would not shift into park without pulling in hard a few times on shifter.
Took back, was told idle was coil, they fixed that. Was told brake problem was speed sensor which would cost me another $135 p&L,since they go bad all the time and the repair had nothing to do with that problem. Now, was told that the shifter problem was internal trans problem and they did not touch trans, so they won't touch. It worked perfect until they put engine in. Am I dreaming or could/are these problems possibly related. I'm not going to give them one dime until I investigate further. Any info much appreciated. Sorry so long, but I think I've given them enough money!! Thanks