I found an old thread on this topic but thats as far as I can get. I have an M3R and the batter just went. How do I replace it, and what about restoring the unit to factory presets? Any ideas?

Replacing your battery is a breeze. You can buy what you need at radio shack. It is a lithium computer battery. RadioShack battery CR2032. Take out the side screws and the neccesary bottom screw and you will see the battery slot in the motherboard. I would buy the battery first so that you can recognize and see the shape before removing.
Steve Ward
firstfruits@bigfoot.com