Most Garages will take the head off, some take the engine out..so you are looking at an hefty bill either way, if the head comes off you will need an head gasket set minimum, then there is the timing belt, probably water pump while its off, all the wet stuff, oil, coolant etc
I dont think any normal garage would touch the cylinder head to remove a turbocharger.
The Audi manual method certainly doesnt mention removing the head, and i'd imagine autodata wont mention it either.
Some specialists on here seem to do it, as its a bit less awkward, but these folk work on the car a lot and have picked up their own tweaks and methods of doing things. Also, i really cant see that much time saved once you've done all the extra work involved in changing the cylinder head gasket, timing belt etc etc. Ofcourse if these bits are needing done anyway then it could pay to have it all done together, but thats not always the case.
Personally, theres NO WAY i would entertain touching the cylinder head to remove the turbocharger. Major engine surgery to remove an anciliary component is something i just wouldnt be doing. I'd rather pull the whole motor out the car complete if it really came down to it.
Audi Specify 620minutes to remove and refit the turbo on the S3, vs about half that on a normal A3.