working day and costs extend tourist visa

Hi, we are travelling around the world and as Europeans we had to arrange our chinese tourist visa in Vietnam. We only got a 30-day one, so we need to extend it once. Do you know how many working days it takes to arrange it and the fee they ask? We are in Chengdu at the time we need to extend.

So we can take care of it in our travel schedule.

Did I understand correctly we bring the following stuff:
1. Passport with current visa (and a copie of the passport and the visa?)
2. Proof of hotelstay
3. A recent 2-inch photo with white or light blue background

Is it all?

Which forms do we need to fill in?