You need to get very recent information on this route. Due to the Tibetan unrest situation and sensitive anniversary dates, earlier in 2009 the Chinese had made off-limits to foreigners, the mountain route that goes thru the Tibetan areas via Litang and Kangding over to Yunnan (Deqin/Zhongdian). That meant no buses would sell you a ticket, or if you managed to get one, you'd get taken off the bus. Private vehicle with guide/driver also a no-go. This was definitely in force in the spring, but I haven't heard any updates on this situation since late May 2009, try posting on lonelyplanet.com's Thorntree forum or virtualtourist forum or other "adventure/independent travel" website forum.