like most people have mention, there is no real harm in cutting your skirt, just measure what you need to cut and check and double check if its wide enough.
i know i dont have an exhaust yet, so we just cut it for the stock exhaust just because the lip sat in front of the exhaust, i didn't want my lip to melt :)
for as the paint, cut and fit, me and my friend did it all in my drive way ahahha xD didn't turn out too bad i'd say can you tell it was a home job :)