Shortly after Boxflyer and I finished filming the 20000Km service on the Wethead RT, a K13GT rolled in for a similar service. This is involved, but there is no great mechanical skill needed. You will need the Service DVD, a decent torque wrench, a vacuum coolant filler, and a few special tools from BMW. Even after buying all these tools, you will probably still save money over paying someone else to do the job.
There are a few points to be cautious of.
1) make sure the cam chain retro-fit has been done on