There are a few good companies doing trips out there but aside from them there seems to be little info in the public domain - a problem with much of China.
Look for a piece to come in AA - once I find the sources.
Wild China are the biggest and most respected homegrown adventure travel operation in China. They may have a trip but it'll cost you considerably more I imagine than doing it more locally.
I'd advise you to just go. Yunnan is not so intimidating - not the more obvious spots anyway. If you need a guide, hire locally and put a few bucks in their pockets. I am assuming you speak Mandarin though. if not, then a guide is harder to find and more expensive of course.