The G-String will be connected in multiple places. First you will want to route the dry guitar signal to its Guitar In. This can come from the output of your wireless. The G-String Guitar Out will feed your first GCX Loop In. After that you will route all the front end effects as normal and anything that will be in the effects loop. Here is a sample diagram that shows the connections you would likely need except for running the wireless and G-String as described above.http://www.voodoolab.com/gcxdiagrams/01 ... _AmpSw.pdf
Where in the signal chain do you want to run the actual noise gate portion (The DEC In and DEC Out) of the G-String? Do you want to run the gate portion in a GCX Loop?
For the channel and reverb switching, your connections will be the same except that you will need a custom made Y Cable. Here is a thread on the topic with a description of the necessary cable.viewtopic.php?f=9&t=3439
I hope that helps!