You two definately need to go to Autozone & write down the CEL (check engine light) codes that the parts guy reads from your cars. I can almost bet the AutoZone guy will tell you that you need O2 sensors - do not listen to him. MOST times it is not the O2s, but just a bit of maintenance that needs to be done.
Post the codes here and ask for advice on what you can do to trouble-shoot & resolve your CEL code issues. Many times it is a simple and inexpensive solution.
If you know how to work a wrench & a screwdriver, you can often do these things yourself in just an hour or two. Not confident enough in your ability? CEGers in your area may be willing to help.
CEG, it's a beautiful thing.