I'm sorry you couldn't get it working Moritz, if Xtext isn't installing, sounds like a clean install of the latest Eclipse is needed (Xtext is an eclipse project, so if it doesn't work, something is really wrong).
OpenSCAD is great for people with a software engineering background and familiar with those concepts instead of "traditional" CAD, in my case I feel very at home with the declarative syntax. That being said, there's lots of good free and commercial CAD options out there (a lot of people swear by Solidworks), I hope you find one that works for you.
Thanks,
Patrick