I did this successfully. make a backup first just in case. I then removed all my contribs and then did the upgrade from disk.
I still have another Mitel SME on the network which I have now installed their latest MAS (Mitel Aplication Suite). Now combines NuPoint Messenger (Unified Mesaging/Unified Communications server) to their Teleworker and Mobile Extention solutions.
So I now I have fully separated the telecom functions from the SME solution.