I make 2 red velvet cakes in the past week, first one went well but second one I'm not sure if I filled it way too much because after hours of completion i could see the cream cheese filing seeping out not thru the fondant but bludging so my cake wasn't smooth. Understand? I think i should of microwaved after the filling prior to filling?? Not really sure where I went wrong?

My question: how long can I have a red velvet cake filled with CC filling out before it's cut and eaten? 5-6 hours or longer? My issue is time... I have a red velvet with CC that I will do for Saturday, if I finish Friday afternoon with it be ok and not spoil by Saturday evening?

As with anything that has Diary products in it, it should be refrigerated. If you are going to finish it that far in advance, your should keep it chilled. As a rule of thumb, cakes with butter/milk/or dairy of anysort should not be out more than 5 hours or so. You run the risk of bacteria setting in.

How do I do that? especially with fondant covering?

did you make a dam? maybe you did not make your dam thick enough to keep the filling in.