Endpoint Protection Small Business Edition

The purchasing manager purchased a 80 user licence for SEP SBE, Small Business Edition. It was a no-exchange nonprofit purchase so we are stuck with it when all we really needed was a subscription renewal for the SEP 12.1 (not SBE) that we've been running for last 5+ years. The serial number for SBE does not work in the current, non-SBE installation. Symantec won't give me an exchange license/serial.

All 80 PC's have SEP 12.1 installed, but license is expired.

So I need a method to:

1) uninstall the old SEP 12.1 client

2) deploy the new SEP 12.1 SBE client.

I see there is an method to deploy using Active Directory Group Policy object, but will this work if all the PC's already have the older SEP 12.1 (non SBE) installed?

Any suggestions appreciated. I'm hoping for a way to deploy other than manually, one PC at a time, removing old, installing new, for 80 PC's.

You should be able to use the 3rd party removal tol in SEPM

About the third-party security software removal feature in Symantec Endpoint Protection 12.1 RU1 MP1 and later

SEPPrep will help in uninstalling and reinstalling the SEP clients. I have used it before and it worked.

SEPPres not only uninstalls third parts AV softwares. It can also be configured to uninstall SEP.

Uninstall third-party security software using SEPprep
http://www.symantec.com/docs/TECH148513

The steps goes as follows:
Install the new SEPM (SBE)
Create new client install package from the new SEPM (SBE) via "Install protection client" option on Home page of SEPM and save them.
Download the SEPPrep and configure it to uninstall SEP using the value "RemoveSymantec" in the SEPPrep.ini (as mentioned in the article at the above link).
Follow the section "How to add SEPprep to a SEP client installation package" in the article at the above link.

Once the package is ready, push it to the clinets via SEPM or push deployment wizard tool.