How hard is it to put a new Campy cassette on a new rear wheel? Do I need to get a special tool? Thanks for any help. I'm trying to figure out if this is a DIY.

Jim

You need the tool with the proper engagement for the spline of the lockring. THese are generally pretty cheap sub 10 dollars. Its very simple to do

What phantomcow said. If you are removing an old cassette, you'll also need a chain whip to hold the cassette while you loosen the lock ring.

It's easy. You need two special tools: a cassette lockring remover (http://www.parktool.com/tools/BBT_5.shtml) and a chain whip (http://www.parktool.com/tools/SR_1.shtml). And an adjustable wrench with a big handle. :)

To loosen the lockring, you need to turn it counter-clockwise. The entire cassette will want to turn as well, so you use the chain whip to hold the cassette in place. And then you can turn the lockring remover with the wrench. It can help if you use the wheel's quick release to hold the lockring remover in place -- it doesn't "sit" very deeply in the cassette, so it's easy for it to pop out unless it's being held in place by the quick release.

Cassette's have keyed grooves on the inside -- i.e., there's only one possible way they can slide onto the hub, so you really can't mess up the process of putting it back on.