DIY gearbox service

[dougisaacs]

Hi everyone, I've just bought my first Audi, a D2 S8 and thoroughly enjoying it . I understand that the gearbox is the weak spot on these so I'd like to do a transmission service. When I read the audipages instructions it seems to say that if you leave the tranny to drain overnight all the ATF fluid will drain out. Whereas, elsewhere I've seen people say that you have to use a specialist pump to change all of the fluid. Anyone give a definitive answer on this please?
Also, I understand that you can't just use any old ATF but do you have to go to Audi for it or is it available elsewhere and if so what is the name / spec of it?
Thanks in advance, Doug