I just thought I'd post some info about VCDS to help clarify things for other new users.
I am fairly new to VCDS myself, but I am a user of some powerful OBDSs' in my professional life.
The main thing I found out was that VCDS is essentially an emulation of the VAG diagnostics machine. This means that if you download the manuals (ELSAWIN etc) for your car, you can follow the steps for diagnosis or replacement exactly.
All the fault codes are equivalent, as is coding and adapting procedures. I know Ross-Tech say to use the factory manual, but they don't actually spell out how useful it is, or how VCDS ties in with it.
When I started working on my Audi, I read many posts on different forums asking various questions, but nowhere did I pick up that using the workshop manual would resolve a large number of VCDS diagnostic problems until I did it myself.
I would advise somebody new to VAG cars to download the correct manual for their car, and get the best version of VCDS lead they can afford (I have a Ross-Tech KII) and then start trying to diagnose problems using both.
Hope this is of use.