Take a look in /etc/fstab
It should have a line for your swap specifying where it is. Then you just check how big it is. If you want to make it bigger or smaller, replace it with any file that's the right size. You should probably turn it off with swapoff when you do this. Using a swap partition is a bit faster (assuming you aren't using one).
Your Red Hat maybe slow because of some extra options being enabled (ie programs you don't need being run, extra features, etc.).