2003 Pontiac Bonneville 2003 Pontiac Bonneville PSI at 120

I have a 2003 bonneville I just replaced the fuel lines in it being that I had horriable gas smell in my car, I took it into the shop and there was a fuel leak, the car almost blew up. I have had that fixed for about 2 weeks now and I started up my car and went to drive it, I got 2 blocks from my house and noticed that my oil PSI gauge is at 120 (all the way to the right side) I pulled my car over and had my husband tow me home. What is wrong with my car? Please help if you can. PS my gas gauge does not work correctly and that will be getting replaced, the oil is in good condition and not sure what the problem might be with the PSI level being at 120PSI