Gunked up PCV wouldn't necessarily indicate head gasket failure. Some engines just have a poor crankcase venting design and they goop up. Saabs we infamous for this, Audi 1.8T, etc, etc. In my experience, engines with lower oil sump capacity are particularly prone to this. Likewise, if you aren't getting it up to temp and running short haul trips, the oil doesn't get hot enough to evaporate any moisture, and get rid of it via PCV - you just end up with oil/water mix condensing in the PCV system. Lastly, synthetic oil is much more resistant to gunking up.
There are a few different ways to diagnoses head gasket failure:
- Oil in coolant, or bubbling coolant (combustion gases getting into the coolant system)
- Water in oil / milkshake oil
- Pull plugs and see if a few of them look spotless (moisture in combustion chamber can steam clean the plugs)