Apple were very thorough with their upgrades. I never did a 128k -> 512k upgrade, however I performed many 512k -> Plus upgrades.

The upgrades always included all stickers and everything to make the upgraded machine almost indistinguishable from the "real thing". In the case of the 512->Plus, the rear case had to be replaced to accommodate the Mini-DIN serial ports and SCSI connector. The 128k and 512k both shared the same rear case, IIRC, so I'd only expect the stickers to be replaced.