It's very easy really, just drop the plastic cover off at the bottom and you can see the pcb board just cliped in place, well worth marking the cables when you take them off.
steve houghton
October 2009
partsarena.com click on data library and search your model it will show you how to do it
howtomendit.com for free repair help, information and advice.
Try fixfault.com to fix home heating systems.