Dead easy,
1. Slide part of the boot lining trim away from the boot opening ( you will see a slash in the material)
2. Pop off the connector with a screw driver, put the screw driver in the slot.. The connector was blue in my case.
3. Unscrew the two nuts (10mm I think). Take care not to drop them behind the trim.
4. Slide light unit out.
5. Unclip bulb housing.
6. Replace bulb.
Look at
http://www.powerbulbs.com/ if you don't know what size of bulb you need....