To add to this, If you are doing it yourself and have the S3, you don't even need spring compressors as there is almost no compression when the nut is half way unscrewed, I went and got some specially for doing my springs but were not needed.
Yes get 4 wheel alignment and new TTY bolts where needed as some are single use and torqued.
I've normally done mine myself.
Springs only on the A3/S3 are a 2hr job, done them plenty of times on the drive.
If your doing the rear shocks as well then its nearer 3hrs.
I've got Bilstein shocks and Eibach springs to go on the SQ5 and this time I'm paying someone as I just cant be bothered this time around.....its costing me £180