i've also got C1 on the 10th of Jan, just focus on chapter 6 to chapter 8(series and sequences, differentiation and integration) thats msot likely to come up but with even more marks available for them.
they are 8 chapters and they are usually 10/11 questions in C1 so no doubt u will be tested on each chapter so there is no place to hide.
just go through past papers and it shud be fine