I have a 3-way switch (top and bottom of stairs) to control an overhead light. The whole landing area at the top doesn't have an outlet available anywhere, so my ex-father-in-law (a DIY type who has flipped some houses) confidently told me he could swap the top-of-stairs switch to a combo outlet that would have a switch for the light and an unswitched outlet.
His daughter and I split and the project sort of stayed half-finished--the switch at the bottom of the stairs stopped working, the top switch worked for the light but no power came through the outlet. I finally got around to hiring a pro, and he put it back the way it was (just the switches) and told me he couldn't put in an outlet there because it's a 3-way wired on a single pole, but that it would be possible to DIY it with a GFI outlet on the bottom/3-way on the top and keep the switch working while adding an outlet.
Does anyone have any detail on how this would be done? I'm decently handy but have only done much more straightforward electrical work. I'm not trying to burn my house down, but it would be REALLY useful to have an outlet available in that area of the upstairs.