Hi Roger,
I'm not familiar with the specifics of your motorglider, but I can say that we designed the EFIS-D10A to be as easy to retrofit as possible. It fits into a standard 3 1/4" hole and, at its simplest, requires power and ground, pitot and static. There is much more that you can do with it, but that's the minimum to get it working.
For more information, see our installation guide:
http://dynonavionics.com/downloads/EFIS-D10A%20Installation%20Guide.pdf
I'm also not sure what the requirements for a unit like this are in Germany. In the USA, the FAA only allows these units in homebuilt aircraft because they are not certified. You would want to check with your local regulatory agency before installing one of these.