Help! Dead Mouse in the wall!

[OnionPatch]

I heard the mouse in there moving around and thought "We've got to patch the holes in the house!" I realized after hearing it continuously for days in the same spot that the sound was one of a mouse trying to jump out of some where he was stuck. After several days it stopped. A week later and now I smell dead mouse coming from that area!! The worst part is that the smell is in my guest room and I'm having guests for Christmas!!!! What do I do?? Are we going to have to tear the wall open?? Is there anyway to get rid of the odor without doing that? Help!!