UKPassats

Hi, as I'm trying to do things on the cheap I want to fit a decat to my 2001 Passat 1.8T myself. Can anyone tell me if this an easy job and do I have to go in from underneath or from the top? Do I need any special tools and are there any tricks to know? Finally, this is going to sound stupid, but where's the dump valve? I've ordered a Forge one but it's going to make an expensive paper weight if I can't find the original!
Many thanks,
Giles