oil pressure on 97 e420
 

okay - I've all lined up to have the oil bridges replaced on my wife's car - it has the usual suspect tap-tap-tap coming from the driver's side of the engine. My local dealership says its the camshaft and wants to replace that, but it seems most likely that the issue has to be the bridges. If it is the bridges, the oil pressure itself would be low, correct? - And - most importantly - (without sounding like a complete idiot) how does one check the oil pressure on the 97 E-420?

mucho thx