I have an smf forum, running on LunarPages hosting.
 I want to create a frontend for the site
 I would like to use either wordpress or Joomla
 I know CPanel has Joomla and etc via fantastico and just wondering... If I install one of these, will it interfere with the way people see the site (as for now it just goes to the smf forum)
 I am completely novice in these matters, but I think I am understanding that, if I install Joomla (or wordpress) I can from there, get myself aquainted with how they work?
 And then I am trying to find info on how to switch it later so when people click on the url, they go to that new frontend, and can select either the forum, or gallery etc.

 So, if anyone could point me into the correct directions to become more familiar with these processes, I would greatly appreciate it.

 One more thing... when I logged in here, I got the popup that I had a new pm, I clicked cancel thinking I would view the message later but, now I see nowhere to check my pms?

I've gone at things the other way around that you, but basically I installed Joomla as my CMS based website, then added a forum to a sub-directory/folder within Joomla and created a menu item to it.

Your way, as far as I know, you can specify a fresh folder for your Joomla to be installed into, thus retaining your SMF forum at the same level from the root. Later you should be able to move things around, but leave that until you learn how to do so I would suggest.

Oh, PMs? Look at the top of each forum page, there'll be a "You have x message, x are new" line, the "x message" is the link to find and read them.