Try a new switch, you've obviously got a bad contact somewhere for going UP. If that doesn't do the trick then you might have to cable trace as the connection will be broken somewhere...
No mate, just pop the switch and surround out from the door card and the switch simply unplugs.
I did manage to get my original switch working again, after spraying some contact cleaner on it, but it soon died after a week. I ended up getting a replacement switch from ebay for about £35.