Well the easiest thing to do would be to get a long patch cable and snake in along or on top of the baseboard from your office to the Xbox in the next room.
If this is not an option you can try some powerline adapters.
You could also purchase a wireless access point, connect it to the switch in your office and connect the Xbox via a wireless connection.
If none of those work for you then all you need is the following and some thinking:
Depending on where the current ethernet jack is in relation to where the Xbox is in the adjoining room the setup would be like this:
Netgear to patch cable to keystone jack in office to ethernet patch cable in wall space to keystone jack in son's room to ethernet patch cable to Xbox. For this you would need two of everything listed above.
If the existing network jack is close to where you want it in you son's room I would imagine that you could purchase a two hole keystone face place and save having to put another hole in the wall. You may also need a crossover ethernet cable in the wall depending on how the ethernet keystone jacks are wired (some provide the cross over function for you). I would suggest that you assemble everything outside of the wall for testing before you commit to cutting holes in your wall. As long as you are carefull with the drywall saw when cutting out the rectangle for the mounting bracket you will not need any drywall skills. If you spend some time researching ethernet cabling using Google you may also find that you don't mind creating your own cables.
Hope this helps.
Edited by eq_shadimar - 9/26/12 at 9:59am