can i shave hollow door

i want to replace my front entry door (with basically the same type/style). i know a pre-hung door is easier than a slab one, but im no carpenter and im afraid to remove the trim and all. is this something easy to do or should i get someone else to do it? thanks

Hi - Need some advise how to recover from a screw-up. I bought a couple Replacement style vinyl windows for a bathroom remodel project - I bought replacement because I didn't want to deal with removing the existing siding, but when I started to remove the old windows, I had trouble with the casement hardware and decided to just remove the entire window and install them as if new construction. I completely forgot about the nail fins being flush with the exterior window edge as opposed to centered. Now I have a problem figuring out how to close back up the exterior. I thought about maybe taking some 2x4 and cutting it down into a 'L' shape so the thicker edge recesses into the gap and the thinner edge laps over the siding, but that seems to be a recipe for water incursion problems. Any assistance greatly appreciated. Oh, I'd also like to know is there anyway to better handle casement window rigging or are casements just not "replaceable"? Thanks Brian