I have been in CD for some time. Getting into the country shouldn't be a problem. Everyone I have talked with recently has had to go to HK to change their visa to a Z visa. Don't worry about it too much, you should be able to get your L visa extended twice for 30 days.

Which university are you going to? Watch out for SIchuan Normal and any of their affliates. Their foreign affairs office is incompetent and has a history of screwing up people's visas.