I am travelling aroung China and will only be able to reach Xijiang in Late Oct or Late December..

Xinjiang covers a large area and most of the places are cold during winter. For instance, Urumqi, the capital city of Xinjiang has the average temperature around -17 to -8 at that time.
In 2013, the Corban Festival is around October 15, so I do not think you can catch that festival in Dec.
For places to visit, I think you can spend several days nearby Urumqi. Then you can go to Kashgar and Turpan. But in my opinion, it is not a good time to visit that place in December and October is much better. Xinjiang in Autumn is the best time to travel.

hi there Dear CHARTASHA ;
first i warmly welcome to kashgar and xinjiang .
some of the my friend give you realy good info about xinjiang ,
if you will be in that area end of Oct that is not bad see all around that place . that is much better then end of December . end of Oct even weather much better then Dec . tempreture end of Oct cool in day bit cold in night .
and corban festival 15th of Oct . best place to see at that time ,turpan , kuqa ,hotan ,yarkan and kashgar , urimqi just like modren other city of china so nothing to see ecept then meseum .
all best regards