A couple of quick basic questions:
Going from Parallels 7 to Fusion 7 I'll have to erase P7, right? What about my Win7? Reinstall it as well? Could I keep myh PC apps/data and only change from P7 to Fusion 7?
You can try and export the Parallels VM disk to OVF format, then import it to Fusion 7. It may / should work, however I never tried this because I'm not using Parallels.