I've installed several conventional skylights, and generally, when you "open up the roof", you invite a little "snake bite".

The toughest part is LOCATION. You have to be sure you're avoiding any obstructions (i.e., electrical wiring, roof trusses, etc.). If you have an air space between the ceiling and the interior of the roof, you'll neet to get inside somehow first. This might mean removing sheetrock from any flat ceiling, since most mobile homes don't have any accessible attic space. If it's a vaulted ceiling, you're closer to the roof decking already, and driving a long drill bit up through the ceiling, then through the roof will give you a locate point.

Pass a wooden dowel rod through the hole, so that it sticks up out of the shingles on the roof. When you climb up on the roof, you'll have your location point.

Long story short, if you're faint at heart, don't tackle this on your own. Call a contractor to install it. It might be worth the $100 or so, since any roof leaks afterwards will be the contractor's responsibility, rather than yours (if he's insured).

If you venture slowly and carefully, you shouldn't have any problems, since the skytube comes with flashing that fits under the shingles, and should prevent any leakage. The important thing here is CAULK AND SEAL, CAULK AND SEAL !!!