well I was recently spending too much time regarding this conversion on 200 20vT
The basics you have to do:
change o-rings to r134a friendly
flush whole system
Change accumulator / drier, costs few tenths of $, of course not available across the pond in Europe, ordered mine from http://www.ebay.com/itm/370919286369?ru=http%3A%2F%2Fwww.ebay.com%2Fsch%2Fi.html%3F_sacat%3D0%26_from%3DR40%26_nkw%3D370919286369%26_rdc%3D1"  but you might get it cheaper, i chose this seller because shipping to EU and global shopping program (has sth to do with import taxes)
Ring set: http://www.ebay.com/itm/Four-Seasons-A-C-System-O-Ring-and-Gasket-Kit-26765-/131037890412?pt=Motors_Car_Truck_Parts_Accessories&hash=item1e8277876c&vxp=mtr"
Valve set: http://www.ebay.com/itm/380850159408"
Didn't bother with the valves and rings as they get too overpriced here after shipping and taxes, I guess my mechanic will have them that were purchased in bulk so probably will cost cents...
Old compressor should work if it is nippodenso/denso or zexel. Not sure which brand is mine but is leaky thus needs a rebuild anyway.
http://www.ibiblio.org/tkan/audi/HC134A.pdf" conversion writeup here, and don't bother with vag numbers as most of them are definitely NLA

mine isn't. My compressor it wetting itself so my a/c mechanic would refill the system every summer, as it is enough for the hot season. I would refill it with R134a. I know it is not good. And he wasn't so happy about just fixing the compressor, he wants to make the whole conversion at once.

I have recently made a list of what is needed. According to pdf file it is most likely nippondenso comressor, so I need the following (vag retrofit is NLA) so I have to get the crap separately

• R134a + oil - my a/c man will have his own. Will cost 30-50$ of local equivalent
  manifold and shaft seals for compressor (might not be needed for some production lots, check pdf) - mine is leaking so i need the set - probably will order from

http://www.vorcz.cz which is close to me. But I have to make sure if it really is nippondenso compressor before ordering. Prices unknown at the moment
Restrictor valve/choke/Orifice tube has to be swapped from r12 to r134a, i.e. 443271191A -> 4B0820177, both available at may places, I will get r134a one from my friend who sells a/c stuff, costs about 10eur
Label stating about retrofit: 357820794 (valve adapter and label kit, NLA) but just the label 8a0101132 seems like it is still available, but I will get one as a part of this set: Santech MT8004, about 20-30 usd on ebay
O-ring set, included in Santech MT8004
Adapter kit for r134a included in Santech MT8004[/q]

and some workforce

http://m.autogidas.lt/sk-nuotraukos.php?section=01&f_1=Audi&f_model_14=200&f_50=kaina_asc&tid=01&rid=26169867#pnr4 gal kas buvot apziuret?

monutotis labai daug vargo, perdarinėti teisingai kainuos, manau tiplsiu į 1000lt
http://www.motorgeek.com/viewtopic.php?f=5&t=55523
mano postai surašyta esmė http://www.audiklubas.com/forumas/audi-c3/audi-100200-pokalbiai/16325/?msg=1571692

jo, balta spalva nekazka butu koks baltas perlas, va tai kitas reikalas. Lietnykus kokius BBS uzsidejai, dar suzeminima camei ir kitas vaizdas. O KU motorai tai tikrai gerai raudavo. Po turbininiu patys pirmi pagal trauka