Thanks for the replies. Still haven't worked out how to get the assembly out, not that I've spent much time on it as yet. If anyone has done this I'd be very grateful for any tips.

The reversing camera was getting a lot of flicker but this was due to the courtesy light power (maybe there is pulse wide modulation here with the computer control of the dimming etc?). Will use an "add a fuse" from an accessory-driven fuse and a 12v-5v converter. At the moment I have no way to power it!