I'm awaiting the FON comments so get them in quick

I've just purchased and awaiting to be told that I can pick it up a RS6 avant for £4k, reason it's so cheap, needs a gear box rebuild...
I've spoken to AMD and they can do it for 3699 but can't tell me what 'enhanced parts' they use or indeed what they are. Do you guys and girls have any suggestions where to get it rebuilt inc warranty?
Pictures and no doubt more questions to follow.
Cheers,
Chris.
P.s I'm also going to the 'ring second weekend in September, house is booked if anyone fancies coming...