If you ask me, take a look at how Jayco Factory do it, then you'll know how not to do it. hahaha...
This would be a fairly basic DIY Job - the only thing that could go wrong is you cut through the roof light wire when cutting the hole - the risk of this can of course be reduced by unscrewing the closest light to where you plan on putting it and having a look at the general direction of where it wire go's into the roof and if at all possible avoid that area.
Oh yes , there probably one other thing that could go wrong, you cut the whole to big for the skylight you bought hahaha... , Then you just go and exchange it for a bigger one and try again. Big like trying to cut your own hair straight and ending up with a crew cut
