Vehicle cd player repair

Good morning

I have a 2004 infiniti with a 6 disc cd player. I am able to load discs into the player but it will not play the discs. Is this something that can be repaired and what would a general cost be? Also the vehicle has a built in GPS and I would like to know if there is a way to update or upgrade the system? I look forward to hearing your response and thanks for your time.

Sincerely

Jason Jones