All you need to do to run multiple applications is to deploy them, there are no settings to reconfigure (unless you want to do multi-homing, if so, search the wiki). As long as there is no name conflict you are OK. For example, a name conflict would occur if you deploy two EARs containing WARs of the same name, or that use the same context.
You cannot deploy the portal SAR twice. The portal SAR gives you the ability to define multiple portals.
For database connection, use multiple *-ds.xml file, one for each connection. The JNDI names must be different for each one. Then each app uses the one it needs.
Thanks for the reply. I was trying to use to portal.sars to test with and I kept hitting a wall. I will try a different route, thanks.