How to fit a pump to a washing machine?

I have a servis M3905W washing machine and its stopped draining the water, to begin with it was making a big clanking sound even when the drum wasn't turning and then it stopped doing that and stopped draining the water from the drum.

I've removed the filter and there is no obstruction there so the next logical thing is that the pump is broken or whatever was making the noise is now blocking it from turning or has broken it.
I know which part I need and where to obtain it from but would appreciate a few pointers on fitting, is it actually as straight forward as it seems to be or should I be carefull of anything at all.