Installing OES 11 on SLES 11 SP2

We originally setup a GroupWise 2012 server on SLES 11 SP2 server without OES 11, thinking we would be able to use SAMBA as our File server later. Our computer consultant convinced us to go the OES route so we now have a SLES11 SP1 / OES 11 server and a SLES 11 SP2 / GroupWise 2012 server.

How hard is it to install OES 11 on the SLES 11 SP2 server with GroupWise 2012?

What steps would I need to take to get this done?

Thanks,
Ken