How do I change the pump on a Hotpoint WMA30 washing machine?

My washing machine doesn't empty the water... after using this website (great by the way!) I was told that if the water comes out when you lay the waste pipe on the floor, then it's the pump that needs sorting. I'm kinda skint and don't really want to pay £100 for someone to fit a new one when they are £20 to buy. CAN ANYONE GIVE A NOVICE SOME TIPS? Lets face it, if I do it wrong then I'll pay to get it fixed, but I'd just rather give it a try.