Comprehensive article here - words& pictures - pictures expand when clicked
http://kaijaks.co.uk/blog/nick/2008/02/10/dodgy-old-boiler
A digital photo before you remove the PCB will give you confidence but I doubt you will need to refer to it.
1) Turn off power
2) Remove lower cover - single screw underneath
3) Drop down hinged plate - single
4) Remove connections
5) Ease PCB off corner posts
6) Reverse order with new board
Peccavi, November 2010
