[ngoma]

I would check closely the vacuum pump-to-head o-ring seal before condemning the head gasket. That large thin o-ring can easily fall out of position, get twisted, worn flat, someone may have gunked it up with sealant, etc. IOW, oil leaking from under the vacuum pump = high probability that it is the vac pump mounting seal that is leaking. You should be able to clean the area, then run the car a bit, and use a mirror and flashlight to look up under there and identify exactly where the oil is leaking from.

If you take out the vac pump, loosen the lower nut first, to avoid breaking off the lower mounting ear. And replace the actuator shaft in the same orientation. It will want to slide out so catch it before it does and replace it with the same end riding on the camshaft. Most easily done with engine at TDC.