Hi,
I've done this in the past by creating my Splash Page in mojoPortal and then moving it above the Home Page using the "Add/Edit Pages" page. A very big thing to watch out for in cases like this is links that point to the root of the site. All links that point to '/' or 'default.aspx' will need to be changed to point to '/home.aspx' or whatever the url of your first 'actual' page is.
It's an option but one that I don't like to use because splash pages are icky and extremely out-dated.
HTH,
Joe D.