I had a servo failure on my c5. Lost all brakes then when I got It recovered by AA it worked fine. No fault codes or warning lights. Had the servo replaced and all good.
I think it'll have to be done at an Audi dealership. Alternatively you could speak to autologics. Various members have used them for retrofits etc so could be knowledgeable on this.
You'll find the steering wheel buttons were often the same regardless of sat Nov was spec'd or not. You're better off just using Google maps or Waze on your phone if I'm honest.