Garage Cabinets, Garage Storage, and Garage Organization

I have a 1997 Ford Aspire, 5-speed manual transmission, 90,000 miles.  

At my last oil change, I observed oil in my coolant expansion tank.  No coolant appears in the oil.  Since this is the case, I assume that the oil is under pressure where it is leaking into the coolant.  Having said this, I suspected the head gasket was cracked where the pressurized oil makes its way to the top of the engine.  I pulled the head only to find no obvious head gasket cracks or stress.  The head and block, where they meet, looks good too.  

I am stuck.  Should I replace the head gasket not knowing if I caught a head gasket going bad very early or replace the head and gasket?  I guess another consideration is that the block could have a problem around the oil pump?

One final thing to add.  Over the winter when the car sat for more than 10 hours, one of the hydraulic tappets in one of the rocker arms sounded like it was sticking.  After re-starting the engine several times when thus happened, the tapping would go away.  This happened 8-10 times.  (Probably not related to the oil in coolant?)

HEEEEELLLLP.  Thank you,  Doug