How hard is it to remove a casset and install a different one? My dilemma is that I'd like to get a King Disco rear hub for my trials bike and my Joker. But I run a road cassette/derailler 8 spd. on my trials bike and a 9spd mountain on my joker. Its not very economical for me to buy two King rear hubs so I'd like to find out what kind of tools I would need on install/remove a cassette.