I've got a BEC 7402 GTM router/modem combo that has been giving a bit of a hard time with my xbox live. I'm currently unable to send out party or game invites due to my router NAT type being set to moderate. I recently contacted my ISP about the issue, and I was told that changing my router NAT settings from "Moderate" to "Open" would restrict all computers in my home from being able to access the internet. I'm having some trouble believing this, so I did some research and found that there are several methods to configure my router and potentially fix this issue, however I'm a little hesitant to do so. My dad has his own custom config settings for his work (VPN and such) That I really dont want to mistakenly wipe out.
From my research, these two sites seem to be the most informative. If I were to either attempt to configure my NAT settings or try the "Port Forewarding" method, would there be any major concerns for me?