Q: Fuel Pump replaced now car won't start 2007 Saab 9-3

I went to the mechanic because my car felt like it was stuttering at start and while driving. They told me that my fuel pump was leaking and needed to be replaced. After this was done my car would not start up very well. This start up issue is different from my previous issue. I didn't have this problem before. I went back to the mechanic telling them that I never had this problem. They told me that it was the fuel injector now. Because they changed the fuel pump the pressure ruined the fuel injector. I have a feeling that they replaced a part that wasn't needed and that they may be using parts from my car for another saab in their shop. Now they are putting used fuel injectors in my car. They say it will take weeks for new ones to come in. They don't normally offer used parts or want to install used parts. How can I tell if this mechanic is screwing me over. I've been going there for a few years. Now that the owner changed the service have also changed.