I have been in China
in Sept.
My H-1B was also expired and in the process of applying for one-year extension(still didn't have it). EAD actually isn't needed. But passport and AP are a must.
If you're not a Chinese citizen, you'll need a visa. It can be obtained through mail in chinese consulate in US (New York, Washington DC)
Other than that, there is no trouble. Since my passport still says F-1(my status when entering US), I was sent to see officers and waited for about 15-minute in US customers. But this is just routine.
In short, nothing to worry.