Does the noise die down when the fluids are all warmed up.

Sounds like worn tappets. The tappets start to crack and deteriorate and the oil gets though the minute cracks when the engine is cold. Once warmed up the tappets expand with the heat due to them being rubber or what ever they are made off and stops the oil escaping.
If the noise doesn't go away when warmed up they need to be replaced.
Speaking from experience from my old Mitsubishi FTO's. It's an expensive job.