Hi Charles K-
Might be worth a trip to get the lay of the land, then come back for serious photography. Late September is pretty much the best time to visit. Weather patterns tend to be settled in an "Autumn Mode."
For years, I did that with my various "hiking cameras" then returned with my Mamiya 7-II to get serious.
These days, I use my 5D-III or my Oly EM-5 with some superb primes, and use Photoshop to help after the fact.
See attached, of various vintages.
By the way, some of the pictures above Wengen, on the Männlichen to Kleine Scheidegg Hke ( referred to by old hands as the Grannies' Walk) were taken in the last week of September, 2009. Stunningly clear weather. Not sure if they are among the attached...film has problems with EXIF data from scans.
Go and have fun... Come back for serious photography.
Look at this thread, where I focused on mountains:
www.myswissalps.com/fo rum/topic/photographer s-going-to-switzerland-in-december.
Scroll down for about 30 images of varying technical and compositional quality.
These two threads give some idea of the variety that is readily accessible if you use public transport and get out of your car...which, by the way, often cannot go where the trains go: