You could get it serviced by ZF in Dortmund, admittedly a bit far from Spain, but looks impressive. And they did build this transmission in the first place.
http://forum.a8parts.co.uk/showthread.php?t=338
Or if faced with a £3k full rebuild, and your car is LHD, its a painful option but you could do a direct conversion to Getrag 6-speed manual with all standard factory parts. If you still have the old car you could bring that one back to life as well.
The most expensive part, the 01E transmission, is now so cheap and the 6-speed 4WD version is found in A4s and A6s. In the UK I bought a 2002 01E from a A6 TDi for just £200. Also the 01E is arguably the toughest Audi manual transmission to date.