I have the Xbox version, I found Reyda's Necklace before I started the quest. Now I can't progress because it leads me to the bones but doesn't register I have the item. I also can't get rid of the thing. I know the PC version has a fix, but can I get rid of it on 360? Will killing Narfi do the trick? Anything?

My guess would be no, but I have never personally tried. This is only one of a number of quest related items in the game that get stuck in your inventory if you pick them up prior to receiving the related quest. Your best option would be to reload a save prior to picking up the necklace (assuming you have one).

No, unfortunately, I don't have one. But, oh well. It's only a half pound. One time I got stuck with three Red Eagle blades in my inventory after I had completed the quest. At 12 lb a piece, that was a problem. But I found that they can be equipped to a weapons rack if you old them while activating it. I'll figure out something, or just ignore it.

Quest items weigh nothing, despite the indication in the game that they do. This used to confuse me too, but as long as item is a "quest item" (can't be removed from your inventory) its weight is zero. To confirm this, try temporarily sticking everything in your inventory (that can be removed) into a chest or other container. The total weight of your inventory will be zero, despite still carrying the "stuck" items.