3l 92 v6 intake manifold questios

[Tysann]

I just pulled the intake manifold off due to a coolant leak.i couldn't see the source of the leak or any indications of leak. All three green everywhere on block. I got all new gaskets hoses and thermostat stuff going to do valve cover gaskets too.
I saw some black in the intake Maybe from blow back oil from cylinders? Should I worry or what? Anything else I need to do before it goes back together? Do y'all use dry gaskets? Looking for heads up on it before I reinstall