Hello Bigtree and Don,
thanks a lot for your answers and your help so far. Yes, I tried to get in contact with Doug Baker from Hagensborg but I was told that he's out of town for a while. So I just have to wait a little.
Bigtree, do you know the area on the pictures on the following website:
http://www.flickr.com/photos/41039231@N00/sets/110051/
These images impressed me a lot; places like these are just what I thought about to go.
Of special interest for me would be the first book mentioned by Don: The Bella Coola Valley & Vicinity: Hiking Trails & Routes
If there was a possibilitiy to get a copy it would be great and help me a lot to plan my trip. I would of course be interested.
One more question: Since you know the valley which time during summer would you consider to have the most stable weather?
Once again, thank you for your help!