Hi Vaughn,
Here's a site with many MB codes:
http://www.geocities.com/MotorCity/Speedway/5350/mbcodes.htm
806 says "change of modelyear last figure shows new modelyear"; I'm not sure exactly how to interpret that.
873 appears to be for heated front seats; it doesn't list the W124 with that code, however, since I know you have heated front seats, it must apply.
(just noticed that you've already been to the 'code' site)