I had one of those nasty things locked up on an A6 that I was working on...it was a NY state car with 200k, and everything was seized as you can imagine, especially suspension stuff. In any case, mine was so corroded, that it was truly impossible to get out without drilling. Schwaben makes a tool for just this purpose with a guide, drill bits, etc. that did the job, but it literally took me a few days off and on to not get too frustrated with the slow progress. Supposedly, you can use the tool with the suspension in place, but I couldn't imagine the stiff neck and shoulders that you'd get without having it out on the bench like I did. Plan on 5-6 hours of slow drilling once it's in a position to work on if it comes down to a drill-out solution. Definitely buy the tool as you'll never get close to drilling it out straight without it.

A few notes, you can leave the top bolt in if you take the entire unit out at the top hat, but you can't get the top arm bolts out without removing as they'll foul on the fender. Also, don't be tempted to try to pry the split open at all to try to free up or get penetrating oil in there...if you crack that, you'll be replacing it (ask me how I know on another older Audi project)...

Good luck and be patient!