Is it okay for cork to look a bit "moldy"?
The cork is normal.  Over time, some of the pigment chemicals will embed themselves in the surface of the cork, starting by the edges.  To my eye, the resulting zone has a bluish brown color.  For a full red, the cork will turn a brown-purple, and eventually black.  All of this should have no relationship to whether the wine is still good.

Some things to look for that will signal a bad bottle:


A change in color of the wine (e.g., pale yellow turning deep gold)
Indications that air entered the bottle or wine leaked out
The smell or taste of wet cardboard in the wine
An ammonia-like smell from the wine
A vinegar taste


Hopefully none of these applied to your wine.