Leak around bathroom skylight; purchase or not?

Probably not worth considering unless at a healthy discount already.

At the very very least, pull the trim ring (on the inside) around the skylight and inspect what can be inspected. My hunch is that you'll have no trouble deciding to walk at that point. At least on my motorhome, this inspection would involve the removal of a total of four little screws and maybe five or ten minutes total.