Does The Undead Nightmare Disk Let You Play It With The Red Dead Redemption Disk In?

In a nutshell, I have Red Dead Redemption for PS3, and I've been trying to get the Undead Nightmare Pack, with the 2 other multiplayer add-ons. If I installed the disk version of the pack onto my PS3, would I need to use that specific disk to play, or would I be able to select it from the menu when I have the RDR disk inserted?