realwahl - 12:16 pm on Mar 31, 2011 (gmt 0)

Thank you very much for the answers. I solved canonical problems, set 301 redirects (hope without errors), set the canonical tag... and went live yesterday. Till now, it seems ok.
I will let you know about the traffic changes (SERP positions) in about 1-2 month (to allow Google enough time to digest the change).