My understanding is that the aircraft needs to be put back into phase 1 testing for 5 hours, making the appropriate logbook changes to reflect a major change, updated weight/balance, etc.
A buddy and I have contemplated trading props for 5 hours. He's got a fixed pitch metal prop and is curious about wood props. I have a wood prop and am curious about flying behind a metal prop. All we need to do is trade everything from the crankshaft flange forward, do the paperwork, and we're good to go...