Just a heads up.... Ford Truck Enthusiasts 7.3L forum, Ford Diesel Power, Powerstroke Army and Powerstroke Nation will have more 7.3L guys around for tech support for future info....
The GPR is the Glow Plug Relay...If you can hear it click then it is working. ICP is Injector Control Pressure. The IPR(Injection Pressure Regulator) controls ICP. You can do a google search for powerstroke acronyms and should come up with the list of the common ones for the 7.3.
What exactly do you mean by hard start? Is it turning over slow, is it stumbling, misfiring, or running rough before smoothing out? Is it just taking longer to crank before it fires? Are you getting any kind of smoke after it has sat for awhile? What color? Does it smell like unburnt fuel if its smoking?
How old are your batteries? Have you checked the voltage on each battery(pull the cables so they aren't connected)? How old is your starter?