UPDATE:
For those that wanted the definitive answer, I did the update (from 9.5.3.3 to 1.0.1.2) and it worked without issue. Make sure to follow the Admin Docs, stop the MTA from accepting new messages (Admin -> HOST-> Configuration) Select server, then look athte MTA box and select teh RADIO button "Do not accept incoming mesages", then go and do the upgrade (Admin _> HOST -> version ->UPDATE tab). The docs say to download however, I select the INSTALL (after selecting the version).
It seemed flawless. Took a bit, about 20 minutes to download (it was about 800 MB worth), then another 10 to 15 minutes it did it all.
Make sure to switch the MTA back to accepting email.
Thanks,