I just took my mio apart because I will have to replace the screen and I wanted to see how hard it would be. Unless the board has broken, you should be able snap the plug back in. You will have to open the mio to do this. They designed the mio so that the plug is easily replaceable. And so is the screen and battery.
You will need a very small philips head screw driver. I got a cheap set from an auto supply store.
Be sure and turn the mio off first using the switch in the back of the unit.
Good Luck
Belisarius
September 2007