Tony is just trying to get an overall picture of the engine. Compression would obviously not impact oil pressure, but if the copression readings are low or vary greatly it might be another tick mark for going in to the lump.
I second the suggestions about further evaluation before stripping the engine. Oil and filter first, then introduction of a known good gauge during cold and hot running. Pain in ass as it might be, the removal and inspection of the pressure relief valve and spring, yada, yada.
That is of course, if you don't hear lots of whammin-n-frammin. A highly technical term used only by "those in the know". LOL In that case hard road testing and such could just exacerbate what ever problem there is.
I would go so far, since the car is new to the owner, to drive it at least enough to identify other problem areas. Transmission function, drive shaft clanking, rear axle noise/rear brake function, that sort of thing. Once everything is taken into account a better decision can be made about expenses, down time and overlapping repairs.
Jack