A pre-hung door will not need any 'adjusting', unless it was manufactured wrong. It should not need planing or to have the bottom trimmed. It's pre-hung, you can tell just by looking if it's going to need anything major.
The best thing to do (not the fastest or easiest) is before installation pull the door from the jamb, remove hinges, sweep, jamb weather stripping, and any other hardware. Seal, stain, and top coat the door. Make sure all six sides, hinge mortises, lock bores, etc. are sealed. Seal and stain the jamb completely (seal back side also) but do not top coat.
Reassemble and install. Plug screw holes in the jamb, touch up the stain, then top coat. Touch up the door itself at the same time if needed.
If a wood door has any real exposure to the elements it is far better to paint it rather than stain and clear coat.
I have installed thousands of doors and operate a custom door business. Take this free advice anyway you want.