This isn't really to do with Linode, more important is what webserver you have running on your box.
Background
Plone runs on a standalone application server called Zope (hence why your site is coming up on port 8080, that's actually Zope). The typical practice is to proxy your Zope server behind a webserver such as Apache.
Solution
It looks like you're using Apache (I tend to use nginx nowadays but that's another story).
You'll need to add a special rewrite rule which will allow apache to "know" about the Zope server running on port 8080.