The Night Mother shall wrap you in her cold, loving embrace...
I have no idea of the glitches on the ps3, but it may be exactly that. If it is a glitch, you're pretty much stuck. It's happened to me before on a different quest. Also think about clearing your cache if that's possible on the PS3.
As far as the expansion goes, you can try any game store, such as Gamestop or EB Games (same thing lol). If all else fails, order online at gamestop.com
Sorry if that's no help, but it's all i got xd
...And may Sithis have mercy on your soul.