I haven't tried but I think you could build by overlaying the extracted source for the SP over the strucutre of the original versions layout. They matchup as far as I can tell but there might be a few files you don't want to do this to at the root. Has anyone tried yet?
That said thou he sould be able to stop SQL Server from starting in services automatically ad be able to apply SP thereafter without causing the lockup. He might have to enter Safe Mode to set SQL Server startup to manual.