The screws on top and side come out easy enough. Its the one on the bottom where water sits that will give you a hard time. Try it by hand but don't let it strip, if that doesn't work, try an impact wrench with a big ol' phillips bit, if all else fails, pour some Jack on the sitch and get out the grinder. Fortunately, its the one you'll never see (unless you're parked on a mirror). Re-drill and tap in a new location.