I've got a Trek 1000 that I'm considering upgrading from its current Sora 8 speed to an Ultegra 9 speed with this set of components from performancebike

http://www.performancebike.com/shop/...988&Store=Bike

Any advice on doing this? or should I do it piece by piece?

And can anyone provide a link for the best way to determine what size of rear cassette I should get?

Thanks!