Reflowing is an attempt at resoldering the existing pins, sometimes when the PPC chip itself is okay this could work. It's worth a shot, ask JJ at Amiga Center what he charges for a reflow attempt. I believe I paid € 150,- euro for mine, but that included fixing the 68060.
Sometimes the PPC gets damaged by applying pressure to the cooler when placing the card in an A4000, in that case reflowing will not help.
Repairing could be worthwhile, if you have a source of NEW PPC's. Reballing them (re-attaching the lead balls at the bottom om the IC) is too expensive as they need a custom made raster.