My wife and I flew from Lijiang to Guangzhou via Kunming. Kunming is a reasonablly sized airport with very primitive security measures. I think when we transfered we did not go through security again, and just ended up in the waiting hall (which seemed to be shared by all the China Southern and some other domestic flights). Both flights we took out of Kunming were 30 minutes late or so, but probably not wise to count on that. I would think that an hour would be fine, perhaps more to allow for flight delays inbound.

As for the tickets themselves, we have always purchased them from a travel agent in China and had them delivered to us once in China. There may be a travel agent that can do intra-China tickets. Air Brokers was able to do a few intra-Vietnam tickets for me. If it's China Southern they must have a ticket office in LA, since they fly to LAX. That won't help you if you're not in the U.S., of course.

You'll have to listen very carefully to gate announcements, as the English there is terrible. My strategy was to stroll around looking for somebody local (or apparently fluent in the local patois) on my same flight and watch what they do.

I can't help you with the changing of tickets/flights. I haven't had much trouble changing flights on the same Airline, but given that it's China any transfer to a different airline is likely to be brain surgery, perhaps followed by a comedy of errors.