About the server certificate
Can SUSE Manager use a third-party SSL cert?
First of all, this is not supported.
That is not trivial, as you have some places and subsystems (jabber etc.) that need to be adapted in configuration. There is a tool called rhn-ssl-tool that helps a bit. But there is also the statement that it is the best to use a root-sub-ca and not individual common server certificates. And this makes sense if you think about server renaming in the whole lifecycle of a SUSE Manager. This means new common server certificate etc. Right now the setup is that the public part of the root-CA is put onto the clients, so that new certificates from this root-CA are accepted by the clients w/o touching them.
An externally provided certificate would need to be injected into the setup workflow. This ability is not provided.