For a remote session you would need to open a case with technical support.
There are instructions for changing the port for IIS here:
http://support.microsoft.com/en-us/kb/149605
If you change the port, you also need to change it to the new port in the SEE Management Server Configuration Manager.
If you prefer using port 80 for SEE, either right-click and disable the Default Web Site in the IIS Manager, or use the above instructions to change the Default Web Site port. You should then be able to right-click and start or restart the Symantec Endpoint Encryption site in the IIS Manager.
You may want to try uninstalling and reinstalling the SEE Management Server. I have seen two issues in the last few days where the symptoms were similar, and they were actually the result of a failure to properly create the IIS site.
Uninstall the existing SEE Management Server, and on the reinstallation, choose a different port number (not port 80, maybe try port 8080) when it asks for the IIS information.