You can search Chinese train schedules in English at http://trains.china.org.cn/. However, for Guangzhou-Shenzhen, I wouldn't even bother: there are trains every 10 minutes or so, and the travel time is just over an hour. Just catch the subway (Line 3) from the airport direct to Guangzhou East station and take the next train from there.
The only catch is that you're landing in the middle of the night, the first fast train from GZ East to Shenzhen is at 6:15 (although there are slow ones from GZ "main" station from 4:11) and the subway doesn't start running until 6 AM. I'd probably crash at a hotel near the airport and get going in the morning if I were you.