Hi,
Here is a link to a video that shows how to dis-assemble a C55DT laptop to gain access to the LCD screen and digitizer (touchscreen).
https://www.youtube.com/watch?annotation_id=annotation_4101045953&feature=iv&src_vid=YIs3z36ltys&v=oexSIN_KsCY
Here is a link to a video that shows how to separate the digitizer from the LCD screen so that it can be replaced.
https://www.youtube.com/watch?v=YIs3z36ltys
Hopefully this is of some help.