Same exact problem here. unit was 4ish years old. My door stopped working entirely and then about a week later it started opening and closing randomly at like 2 am. Scared the **** out of me until i figured out what was going on.
I called Liftmaster and they sent a new wall panel for free...
+1 have had two of these for years. Great units. Also if you have the ceiling height, do the high lift mod on your doors and get them up to the ceiling. Really opens up the space and will allow you to put a lift in if you are a car guy.
Got an XPR-9S-LP installed today. Lift arrived with a few cosmetic imperfections from shipping but in otherwise good condition. No rust, nothing broken, nothing tweaked. Everything is working as expected. I'm quite happy.
No, you have it right. Just remove all the stuff from your old opener - the drive shaft is then connected right to the jack shaft opener mechanism. As long as your spring is in good shape you should be good to go. Don't forget you will need power near the opener on the front wall.