How serious is this and what is cost to fix?

[The Radium King]

well, the oil sounds like rms, spark plug tubes, oil fill tube as noted. perhaps retorque sump fasteners. replace oil fill tube - often cracks. engine noise is most likely ticking lifters (is it a tick?) which is a live with it noise. iif it's a chirp it might be loose spark plugs which would get addressed when you did the tubes. nothing terminal, nothing that requires engine out. do rms and ims if time to do clutch (ie when transmission is off). standard maintenance stuff.

solenoids (or ramps) require that the valve covers come off which requires locking the cams in place to mainntain timing. if he's a porsche tech he should have the tools for this. it is tight but can be done with engine in car (mine was).

however, if you didn't have a check engine light then something is off - perhaps a second opinion unless you really trust this guy. also check your gauge cluster as the cel lamp might be disabled - perhaps you bought the car off a devious individual who disabled the lamp so as to sell you a car with a problem?