Checking fuel pressure is easiest. Ideally you need one of these (Summit Racing® Chrome Plated Fuel Pressure Gauges SUM-800199 - SummitRacing.com
what ever one you buy does't really matter but it needs to be fluid filled to stabilize the needle) and a 1/8"-1/8" NPT female coupler. On the back of the fuel bowl there is a Schrader Valve. Spin out the valve from the port and install the coupler and gauge. This will get you idling and neutral rev'ed fuel pressure but if you install an 1/4" rubber line rated to 100 psi and Diesel you can run the line to your windshield wiper and watch the Fuel pressure as you drive.
For the HPOP oil galleys get a gauge rated for oil and 3000 psi. have your local hose-man or tracktor shop make you a line that will come off the oil galley in the head (I think that it's 1/4" NPT for the hose) and do the same thing. Run it to your windshield wire and watch it as you drive.
An expensive auto scanner will be able to monitor the HPOP but those are big bucks.