The benefits of an AROMA installer would be a customized ROM installation. It can let you choose what apps you want to install, or other features, depending on what the developer adds to the script.
As for porting a ROM using AROMA, here's a basic guide: http://forum.xda-developers.com/show....php?t=1908008
Unfortunately, this guide can't teach you everything. It's very basic. You will have to learn the complex stuff yourself. Also, you can't just copy the aroma-config and updater-script from the ROM you are trying to port. You will have to, in a sense, "port" those too. You'll have to research yourself.