I have a 2005 E500 Wagon that I ordered last year and took delivery of in January. It has the Premium Package that includes the Harman Kardon radio system with navigation, etc. Many press releases have bragged about the fact that all 2005 MBs come w/ Sirius satellite radio and mine has a SAT button but I have been unable to find any activation code to use w/ Sirius.

Source also on CNet

When I spoke to my dealer they wanted to charge me $1,000 in parts (receiver and antenna) plus $300 labor. I certainly don't want it that bad and I feel misled about what the car actually has that supports satellite radio. In researching this further I found a link on the mbusa site that says seems to support the dealer installed option opinion but lists a lower price for the parts:

Any pearls of wisdom? Is there a more cost effective way of getting Sirius integrated w/ my factory unit (no aftermarket add-ons)? A good source for the parts? Any documentation on the installation? Is it a reasonable project to do myself given good mechanical abilities but no special MB-related tools or experience? It seems that the kit includes an unsightly black blob of an antenna that dealers usually drill a hole through the decklid to mount and many owners use aftermarket units. Any idea what the antenna solution is for a wagon? Have they figured out a way to combine the nav and sat radio antennas yet?

I don't know where you live but it would be in your best interest to research this thru a reputable car audio shop and I don't mean Best Buy or Circuit City. Check with local shops and ask them for pictures of their installations and make sure there are nice cars pictured...You may find out in the end that the amount of money the dealer will charge is not that far out of line for dealing with a car as nice as yours. It includes a year of subscription which by it self is worth $150. The problem these days is that good shops are hard to come by. Twenty years ago they were everywhere but with the advent of much better equiptment installed from the factory a lot of shops have closed. Chances of getting factory MB stuff any cheaper is probably not going to happen however it is interesting that the dealer you went to wanted almost twice as much as the article quotes....Find out how much to buy just the equiptment from the dealer and judge what the labor really is going to be...The antenna is likely to be tricky....Needless to say probably not an easy job and I did this for a living for 25 years.....

__________________
83 300CDTurbo 307,000
2005 Honda Element 266,000
56 Nash Ambassador Country Club Special 34,000(under restoration presently)

http://www.peachparts.com/shopforum/car-audio-multimedia/125099-123-install-extreme-dynamat.html

I installed a Sirius receiver in my 2005 E320 cdi. It mounts behind the right rear trunk panel on sedans. You should be able to buy the kit for around $600-700 including 12 months of service. I mounted a small (magnetized) Sirius antenna on the roof which works very well. The MB Sirius receiver integrates with the Command system without needing to be initialized by a dealer. Good luck.

I have a similar issue with the '04 CLK 320 I just bought. Does anyone know of any type of aftermarket installation? Also, is it possible to install an XR tuner instead of Sirius and run it through the Comand system? I already have 2 XM accounts and prefer to stay there.