Allow half a day, need to remove the inlet manifold & drain the coolant. Need a small tube of RTV sealant for the end seals and a tube of Hylomar for the valley gasket.
Get under the car and see if oil has been running down the back of the engine, if in doubt, clean around the sump joint and the block above it, give it a run and check again.
The valley seals do tend to harden off and are known to spring a leak..not too bad, but messy !!
Details for replacement on RAVE under "Inlet Manifold"