Staggering!
Don't do it - how are you gonna check it's been done correctly? You won't have an analyser or anything..
The fan on a condensing boiler is not simply a fume-clearing device, it's a bit more complex than that and has a direct impact on the boiler's safety and efficiency.
Frankly by even removing the cover you've broken gas regs (it forms the combustion seal on this model), and as stated before, the poster who says "just turn the power off" should really know better.
Anyway, how do you know the fan's the problem?
Bunslinger, April 2009