Exactly the same happend to me,
I think there are a few other people with broken springs as well!
I Did the rear springs/shox on mine last weekend, sheesh nice job....
If yours is an avant then there are 4 bolts holding the metal shoch stay to the body, you will need to get this off to remove the spring. See if you can get elsawin (audi repair manual) to help you out.. on (dis)assemby stuff. The Haynes manual only does 2wd and no quats
Some points, the job is easy enuf, all bolts were ok to undo though you may want to replace the bolts & nuts. The shock tower back may be rusty, The Pink/white markings are what you need to give audi - if you want the std springs, Euro car parts helped me no end as there are lots of types of shocks / springs.
If you need any info pm me I should be around this weekend, go some work to do on my web site so do not have time to sort a "how to" at the moment!
if its any consaltion, I had been running around with 2 broken springs! the back it a bit higher now. I put billies on mine as Audi said they were on back order on the OE's
Cheers
Michael