Might need to play Peace Walker as well! I didn't know it was canon so when I read the "what happened before" in MGS V: GZ I got everything spoiled haha!
Dunno what to do really cos I have it lying around in the HD collection... Should I just go play that one first despite having read all the spoiler text or should I just continue with MGS V: GZ and not give a fuck?
Peace Walker is totally still worth playing! I picked up the HD collection recently and went back to it. The Mother Base building alone is still great.
If you're worried about story however, I've played MGS 1 - 4 a few times each and I still have no clue what's going on...