Easiest way that you can do, considering your claim of noobyness, is by going through ROM Manager (app, paid version) and going into the Bugless Beast option under Download Rom, and pick NexTheme from the selections it will give you.
Wipe and Clear before you install, its an option given to you after you d.l the ROM
*Note* I had to Wipe and Clear twice before it ran correctly, meaning I had to install from ROM Manager twice before it worked properly.
and as always.. DO A BACKUP! another option given to you from ROM Manager.
easy stuff
Also keep in mind that when you do Wipe and Clear you will have to start over with placing your apps where you had them as well as the data you have stored in the apps, unless you use Titanium Backup (donate) which will save all if not most of your data in the apps... and I read somewhere that My Backup Pro will also back up your texts.