Hallo!
Maybe I can help a little bit with the installation problems of Ruebelandbahn by translating the most important parts from the docs of the route. First the recommended way of installation (no problems, no danger for your installation of MSTS)
1) You must have MSTS updated to v. 1.2 and BIN patch (at least) 1.7.051922 installed. Default routes aren't necessary.
2) Execute Ruebeland.exe (Don't change the path to your normal MSTS installation!)
3) Copy train.exe and launcher.exe from your normal MSTS installation to the new Ruebelandbahn installation.
4) Start the sim from this new installation.
Now the way to integrate Ruebelandbahn into your normal installation. (If you want to use rolling stock from this route in your normal installation or vice versa) This way requires some manual changes, so backup!
1) Start with step 2 of the instructions above, and let the exe create the extra Ruebaland installation.
2) Now rename the global folder from the extra Ruebeland installation to global_RLB and copy it to your normal MSTS installation
3) Copy the trains folder from the extra Ruebeland installation to your normal MSTS installation.
4) To run the route you must make the last, most important and most dangerous step, because Ruebelandbahn uses a completely different track system not compatible to the default one and to xtracks.
Backup your original global folder by renaming it and rename global_RLB to global. Now you can run the route by starting the sim from your normal installation. When you want to run one of your original routes you must execute this renaming procedure the other way round.
Now the rest of the extra installation isn't necessary any more, but I would keep it until being sure everything works.
It would really be a pity if some problems kept you away from trying this excellent detailed route with its fine rolling stock. (For example the class 50.35 steamer is a very useful engine for all your DR routes.) At first I was a little scared, too, but starting with the automatic extra installation and then transferring the route to my normal installation step by step (I wrote a pair of batch files to do the renaming job automatically.) I've spent many pleasant hours there. Driving a train with two of Stoney's class 95 steamers from
http://www.train-sim-werk.de/ from Blankenburg to Koenigshuette is a real challenge.