When I did mine I marked everything and after the spacer went in it was all slightly off. You just have to check it is off in the right direction and go with it.
Just remember to allow for the spacer when putting everything back together. Had me scratching my head for a bit. I have a Bentley manual if you need to check anything.
Heavy cars need the usual things checking like brakes, bushes etc. With a newer car like what you have in mind then I would think a thorough check of the service history and a VCDS scan.
I have an A6 Avant and love it. Roomier and cheaper than an A4 but with it's own style. I have a remapped 130pd set to about 170bhp. I would love an RS6 Avant which just might be on the cards in the spring.
How deep a restoration are you attempting? http://www.ebay.co.uk/itm/BASIC-CAR-ROLLER-TILTER-JIG-CHASSIS-TILTER-TILTING-LIFT-JIG-CJAUTOS-CT01-/330767963769?pt=LH_DefaultDomain_3&hash=item4d034e9679