I've taken the cover off of two Rapid 100s and had no issues with tight screws--you may not have any trouble. I wouldn't use anything else other than a sharp screwdriver of the correct size. Push down hard as you unscrew. Maybe someone used a bit of loctite (glue) on your original camera's screws?
In my case, the fix for the plates was fairly intuitive--just spend a bit of time looking at the assembly and the problem may be obvious. If you can get the cover off of your working camera, you'll have a comparison. I'd be happy to send you some detailed photos if you get stuck. The plates have one correct position, so there are no worries about misalignment--they'll either be working or they won't.