Modern tactics are to use every radar around via datalink (AWACS, Ground Station, stealthy drones flying ahead). The onboard radar is last resort, but still very capable.

Right, so I wonder what difficulties they are having with the F-16 to retrofit the new package to receive the same datalink.

The US is stuck with older F-16s than the current export models with advanced radar. They're gradually being upgraded with some Block 70 components. That requires the new cockpit so it isn't just a quick part substitution.