CHINA: Visa extension in LITANG or around?

Hello!
We are a belgian couple travelling in Asia. We are now in China and we are facing a problem, always the same : VISAS!

We entered in China the 30th of march and we are now approaching Shangri-La (the 14th april), north-west of yunnan. We are wondering where we could do our visa extension for one more month... ?

We know that in Shangri-la it is possible. But we'll be there in three days, so we don't want to renew our visa ten days before the end of our first month, because we'll waste nearlymore than a week by doing that!

So our idea was to go fast until Litang (south of Sichuan), arrive there around the 26th, and still have three or four days to make our extension. Would be perfect, but we are really not sure it is possible to do so in Litang. Anyone knows something about it? And if in Litang it's not possible to do the extension, does anyone have an idea for us (knowing that we would really like to avoid taking a bus in that beautiful region)?

Thank you very much,

Jo&Max