Hi there,
You can download the install manual, etc at: http://www.unwiredtools.com . They also have a forum for their products. There is a link on the forum to an install someone did on a 116 that is interesting to see as it shows some pictures of the install.
I purchased the kit at Performance Products. They have a website, http://www.performanceproducts4benz.com, which shows a few parts, but they also have a Mercedes catalog that has a great deal of parts and accessories available. The cost of the upgrade was $699, not cheap, but I felt it was worth it to have the improved performance.The upgraded kit performs all the functions of the original unit, ie 4 fan speeds in heating, 5 in cooling, precise control of the temperature - on the latest revision they replace the Mercedes temperature sensors with their own which are better placed and more sensitive, according to them. At any rate, it works well.

Regards,
Richard Wooldridge
'82 300D/4.3L V6/T700r4
'79 450SL
'75 280C