First the list of parts:
Climatronic module - 1718300685
Multisensor - 2118300472
Bracket - 1718300472
Sunsensor Holder - 1718310559
All or some of the above parts will have to bought new. I found Mercedespartsdelivered.com as the cheapest source of new parts.
If all you are going to install is the module and the multisensor, it is a 30 minute job. If you like skinned knuckles and cursing, then you'll want to install the sunsensor.
The very first thing to do is disconnect the battery. Before you do that, unlock the trunk, glove box, and decide whether you want the windows and top up or down.
To install the module, you have to remove the ashtray. The module then just pulls out. Review the following to remove the ashtray:
If your ashtray has a cigarette lighter, you'll have to remove the cover off the front of the lighter to reveal the second screw. Just take a screw driver and pry it off using the left side. Note how the electrical connection fastens into the lighter. The plug goes in at a right angle to the barrel of the lighter. Use a small screw driver at its base to pry it out.
Next mount the multisensor to its bracket. The bracket is fastened to two bolts protruding from the inner fender next to the battery. The connection for sensor is fastened to a nearby cable. Remove the cover and plug it into the sensor.
Installing the sunsensor was a real PITA. I wish I hadn't bothered with it. But if you decide to go ahead:
Remove the radio and the cupholder. Incidentally, everything is held in place by T-20 torque screws. Next comes the speaker grill. The forum has detailed instructions, but essentially tug on each side of it until it pops out. Two metal clips hold it in. Finally, you need to pry out the sunsensor bracket. I used a big long screwdriver. I hooked it under the front edge alternately prying each side until it popped out.
The glove box has to come out next. Remove the metal cover above the door. There are two slots on the bottom of the cover where you slide a small screw drive up to unhook it. Next you take a strong putty knife and shove it into the space between the cover and the dash and pry it down. This required a lot of twisting to force the cover down. I discovered it was glued in!
There are three screws behind the cover, three more for a cover on the bottom, and another four on the lip of the box that holds it to the dash. In addition, I had a 12V outlet that needed to be unplugged. Remember how you unplugged the ashtray.
Now you need to find the sunsensor cable. Look up and into the cavity of the center stack. You'll see two places with masking tape wrapped around the wiring harness. Remove it. You'll need every bit of available space to do this. The cable will be revealed.
The sun sensor just clicks into the new bracket, and its cable just plugs into the bottom of the sensor. Now just stuff it back into its cavity. Unfortunately, I couldn't get it to sit perfectly level. I guess I'll have to live with it.
Now put it all back together. You'll have to synchronize the windows and reprogram the stations in the radio. This little mod worked perfectly, and I patted myself on the back for a job well done.