Sure you can, but if you want it to act like a regular button you'll need 3 frames. The normal one plus one for hovering over and one for clicking the button.
Though I would just make my own button sprites since, in my opinion, the regular buttons don't really look good in games.
And yeah, you'll probably have to change some conditions. But replacing some button events with mouse events doesn't take too long if you just copy/paste the conditions.