dragonair

Hi this is my first post and sorry if I missed a solution on a search..... 2002 C5 Exclusive 2.2 HDI estate rear tail gate window has failed for the second time after an replacement glass 2 years ago. Dealer did it under warrany but probably fitted second hand. Window will not open. Any fix or is it another window - any sources? CD player under the seat - car has forgot it exists again is this a dealer job? Great site. rgds