Doors and Windows - Replacing rotted exterior door frames

Roof overhang did not protect bottoms of door frames from rain and have rotted out and need to be replaced. I know we can buy the prepackaged frames at Lowe's but are we going to be able to do this job or does it require a lot more knowledge than just common sense? So far we have successfully removed toilets, replaced bathroom floors, rewired ceiling fan/light fixture, replaced vent-hood, etc. but this particular job scares me. Any advice will be appreciated. Thanks much. Nancy

Rotted exterior door trim can be easy to repair. You can do it, if you've done all of that other stuff.
(The only problem may be framing rot behind the door trim, which you can repair the same way.)
All that you have to do is smoothly horizontally saw-off above the rotted trim and framing.
Use pressure-treated wood to replace the rotted pieces (except you won't be able to find p-t brick molding).
Seal the ends of the boards and trim with caulk or paint before replacing, especially the bottom to help prevent it from wicking water up into it, which is why it rotted in the first place.
Good Luck!
Mike