I had plugs, engine air filter, and cabin air filter changed along with synthetic oil change and tire rotation with 10 percent discount coupon for around $400. I believe changing the 16 plugs takes awhile ( 2-3 hours). Pricey but not as bad as an oil change on a Porsche turbo S $300.
There is a good DIY (use the search function) for the spark plugs. The change out took me about 60 min and I was going pretty slow. I would also recommend changing the rear differential fluid at this time as well. I have the limited slip in the rear and the fluid was in need of a change at 30k.