My 2004 Neon Chrysler - has approx 157,000.

My 2004 Neon Chrysler - has approx 157,000 kilometers. I went to the garage on Friday to get the CV joint fixed, because my car was making allot of noise when I made a turn. Picked up my car Friday night, left gargage who was closing at :00, when I pulled out of garage, it seemed like they hadn't fixed it, but it made a noise when I made a turn, I also noticed when I put my foot on gas it was slipping. Noticed my speadometer wasn't working, weird, got home. Thought maybe the car has to settle. So when I went to go out in the afternoon, when I put my car in reverse it wouldn't reverse right away. Then I drove down to store, and car was skipping, came home, called garage but they were closed, so I left a message. So I drove it back there today, didn't feel comfortable becasue the RPM was going to 4, I though what did they do to my car? They just called me and said Murphy's Law, it maybe the transmission, but they still haven't diagnosed the problem. How can that be. Did they do something wrong when changing the CV joint. Please help me out here. I wouldn't want them to think oh she a woman. I always have my car serviced, but I went to a garage here, because I didn't feel comfortable going 1hr drive to get the cv joint fixed, and now I havbe these problems. What do you suppose the problem would be? You expertise would be greatly appreciated. Is it electiral etc. Thanks
Donna