Setting up an RGH console requires soldering skills. If you aren't experienced, it's highly recommended to have a professional installer do the work to avoid "bricking" (permanently breaking) your console. Software Setup: ConsoleMods Wiki
RGH consoles can run XBLA titles and DLC directly from the hard drive without needing a license check. xbox 360 games rgh
You can use any 2.5-inch SATA hard drive up to 2TB to store hundreds of games directly on the console. Xbox 360 RGH: A Detailed Examination Setting up