About the two tests:

Compression test will tell you whether you have leak cylinder or head gasket or not.
The oil gallery pressure test will tell you if you have engine oil leak or not.
You should have the oil pressure test first. If there is a leak, then follwed by testing the frequency of the engine noise, you will tell whether it is camshaft or crankshaft problem or not.
You can mention the tests to the shop person. But they should know what to do. By the way, if your car is not under warranty, do not go to dealer.