Final Cut Pro won't open

Hi. I seriously need help.

I downloaded plug ins from Pixel Film studios. They said I need to close Final Cut pro and open it again, and my plug in will be there. The first plug in I got worked, and I used it successfully. The second one led me to doing the same process, and now Final Cut Pro will open for literally (no exaggeration) 1 second, and then close. This is very frustrating. I have now gotten to the point where I wanted to delete FCP and reinstall, and my computers says I can't drag FCP into the trash because some extensions are in use. I've now been in front of my computer for 2 1/2 hours and I haven't gotten anywhere. Please help me ASAP.