Not done it myself because my controls aren't the same as yours, but apparently you can get to the bulb by giving the knob in the centre a good tug (oo er missus) and it should come out. You should then see the bulb behind it but it's a git to get to, so use a small piece of hose and push it over the bulb, then slowly work it out.
Wont be much help on your other problem i'm afraid.. could be a fuse, switch at the door, switch at the lights themselves, bulb, broken wire etc etc. You'll just have to eliminate one at a time i think
