For me this was one of those "grit your teeth and do it moments" I did the same things. New holes for new light fixtures. I just used screws that where no longer than the originals and just did it.
The old holes where hidden by the new fixture.
Besides if you where to put a screw into a wire and make a short the fuse or breaker should pop right away. I've done that with 110v wire in a house, put a saw blade right through a wire. A pop, a few sparks and a black mark was all that I got out of it other than a blown breaker.
I don't really know of any alternative than to just do it. You could shut down all power in the coach and then do the work. Then watch really carefully when you turn the power back on.
2008 Georgetown SE 350DS BunkHouse