h4x0r

I just bought an used 2000 Audi A4 1.8t Quattro from a private party.
The radio isn't working. I checked the fuse and it's good, but I noticed something.
It seems like they had a "Remote Start System with Responder Technology" installed on the car. I couldn't find the onboard diagnostics plug(?) under the steering wheel. They probably messed up with the wires and left one loose for the radio. [I was thinking on buying a new radio, but this one probably works]. So I have three questions:

1) How do I remove the panel under the steering wheel to have access to the wires?
2) Where can I find a diagram or other helpful guide for the wires?
3) What's up with the onboard diagnostics thing? Should it be there? [it might be there hidden under the panel]

Thanks for your help!