1988 Ford F-150 Intake manifold and/or head gasket replaceme

Engine Mechanical problem
1988 Ford F150 V8 Two Wheel Drive Automatic 166k miles

My truck has developed oil leaks from what I am told is the intake manifold. There is visible oil pooling in the front/upper area near the distributor. Engine performance is also affected as it starts OK but begins to run roughly after warming. I was told that was due to coolant leaking into the intake. I want to replace the intake manifold gaskets but I am unsure if this will require head gasket replacement also. I have searched high and low for repair procedures on the internet to no avail. Any help at this site?