how do I replace a intake manifold gasket?

I have a 89 mitsubisi pick up and i have water in my oil. Te truck will turn over but will not start. The oil is gray in color and shows over full on dip stick.
Yhe truck ran hot on me on the way home. I checked the water in the radiator and filled itup. Went to check it this morning and it would not start. I looked under the hood and a little water was leaking around the water pump.Still will not crank. when I checked the oil it was light gray in color andshowed over the max mark on the oil stick. I was told it may have busted a manifold gasket thank you