How do I recode 'new' instrument cluster to my car

[GH77]

Hello again,

I've got a hold of an instrument cluster to replace my own which is showing signs of wear and tear. Both are from FL cars, my own being a 3.7 and the donor being a 4.2. I understand from reading other posts that the immobiliser is built into the cluster and that I need to get it coded to suit my own car otherwise it won't be wanting to start. Couple of questions:

1) Do I just walk into Audi dealer and ask for my car's immobiliser code?
2) Do I then fit the 'new' cluster and use VCDS / VagCom to give my 'new' cluster my own car's immobiliser code?

Doubtless these two questions will raise others so I thought these would be a good place to start.

Thanks.