Originally Posted by Chris_F

Piece of cake. You'll need some tools, one to remove the nut thing that holds the gears on and one to hold the gears (a chain whip, looks like a piece of chain with a handle, although I use an old chain and it works). Most bike shops will be able to sell you the tools.

All you do is remove the nut thing with the special tools, slide the old gears off, slide the new gears on, tighten the nut thing and you're done. Once you have the tools you can then remove and clean your rear cassette any time you wish.

I believe some rear hubs simply click less than others, probably no big deal.