Please help just pickedn up my 2005 mercury mountaineer from repair shop and now my abs and awd locked lights on after getting a valve gasket cover replaced. what could be the cause?

car stopped on me 3 times on my way home from work, managed to get it to a friends house after letting it sit 15min between shut off. Came back 2 weeks later to see if I could get it to a shop and it started right up and drove 2 miles without cutting off however I did notice a funny burning smell looked under hood and it was a little smoke coming from under engine. Told the receptionist everything that was going on and she told me they'll give me a call to let me whats going on. I was later told that the car never shut off on them and they don't know why it did, and stated I must of got hold of some bad gas but I needed my valve gasket cover on the right side replaced that's where the smoke was coming from and it could catch on fire so I agreed to pay 500 to get that replaced. I picked my car up and not only do I have side swipe marks on my car that they don't know where it came from but my abs light is on and awd is locked / disabled and its saying in the dash see owners manual. I have 3 children and its close to Christmas feeling overwhelmed please help.