I bought a 1990 Ford Probe to be my sons first car.?

We had the garage give it a full tune up, oil leeks repaired and it ran great. While I was at work, my son thought he would clean it up inside and out. It looks great, unfortunately he also tried to clean the motor. He used engine cleaner and a hose. Now the car runs like crap, no power and it misses like crazy. We took off the distributor cap and it looks dry but could there be water somewhere deeper that we can't see? What could have happened to it? Do we need to take it back to the garage or is there something we can check and fix? To be honest, I am a single parent and it took all I could borrow and all I could charge on my cards to get the car, motor looked over, tune up and oil leeks fixed and replace the window so I don't have a lot of money to do anything expensive and I am praying that we can get it fixed rather cheaply. Any suggestions greatly appreciated. Thanks