I just got a block heater installed on my 06 HCHII last week. The dealer charged me $119 installed, which included the heater, new antifreeze, and labor. I had it done at the same time as my first oil change, and it took about 1.5 hours to do both together.

Edited to add:
The part number of the block heater is: 8105108 08T44-SVB-100 (From my invoice). The dealer charged me $59 for the part.

It didn't come with any instructions, or user data though. I don't know how long I will have to plug it in to warm up my engine to operating temp when its 30 degrees outside. I plugged it in for 5 hours one day, and that brought the temp guage up to 5 bars, but it was 70 degrees in my garage.