I fitted my own to a Volvo 740 but looking at U-Tube videos it looks rather a more complicated job on an Audi but I am surprised no one qants the job. Have you tried your nearest Audi dealer?
Years ago I fitted a set to a Peugeot 405 and they made quite a bit of difference, it made an already good tow car even better! Have you tried contacting the the MAD suppliers to see if they have a list of recommended fitters?
What makes you think that you need MAD springs? A Q5 is about the last car that I can imagine would need them. Are you sure you aren’t overloading the back axle in any way because that’s the only reason that I can think of?
BAX