Intake manifold crack

Hi- I made a donation (#111646-0) and the program would not let me back to ask my question on the ask a question page.
I wiill try to send it again.

I have a 2002 Buick Park Ave 3.8L with 75,000 miles from a recent purchase. On a cold start during warmup the intake manifold starts to leak oil from about a 3/8 inch crack on top that is not visible. You can tell the length from the oil seeping out. After it seeps out about 1/2 teaspoon the manifold warms up and seals the crack. It will not leak again until the engine completely cools down like overnight.
1. Does this have to be fixed or can I just mop up the oil every few days?
2. Is there some kind of sealant that can be applied over it to seal it?
3. If the intake manifold has to be replaced how much will it cost?

Thank you very much.

Kent Huggins