I went back to Big Al's today to talk to them about the shrimp. They're guessing that based on what we described, and pointed out a similar shrimp in their tank that our shrimp is pregnant. She may have gotten a little agressive because of that, and that it also could be she's ready to drop. Most times all the fish in the tank leave her alone, and say away from her little favourite area. The snail may have just wondered through. We fed the tank, everyone seemed to calm down and had a peaceful night. The yellow thing was gone by morning, and when we looked at the other shrimps at Big Als, they all had different colours. Could have been something she ate.
Usualy we research before buying, this was the first purchase that we hadn't found much information on. But Big Al's people said we should be ok....here's hoping. Just not sure if I'm looking forward to baby shrimp or not...