I know both are possible... We have not setup a server-wide certificate but it is just a matter of changing some of the paths in the secure httpd.conf file and maybe adding some symbolic links if you want it to work like Alabanza does.
As for the Equifax certs, you will need to add their certificate plus yours to the server and then add a line in the httpd.conf file to pickup their certificate. This is because they piggy-back off Thawte's root certificate so you don't receive an error with your browser. Instructions are on Equifax's web site.
If you need more detailed instructions let me know...