reschedule citizenship interview

This is the only time USCIS is faster than I expected. I got citizenship interview on 01/10/2013.

Howver, I plan to visit China early April. In order to save some visa trouble, 

Q1. Is it reasonable to write a letter to USCIS rescheudling interview after I am back from China (4 month later)? If so, how? by letter or someone mentioned infopass?

Q2. Is it possible to show up 0n 1/10 and only do interview part, but not turn in Chinese passport and have a in-person reschedule with officier? Does it sounds like "you-got-be-kidding" request to them?

Thanks