I swapped out my old PCV valve for a new one, and noticed that there was a significant amount of oil on the old valve. Should this oil be present? It seems a little odd to have oil here.

 

How much is significant? I know you're supposed to lube the o-ring with a little oil.

 

Why would it be odd? That is the crankcase ventilation. If there was a lot of oil then the valve inside may have been seized and was not releasing the oil/vapor back into the manifold. If you want to keep that oil from making it into the manifold then look into one of oil catch cans either as a product or there is a pretty through DYI with parts from home depot here on the site.