If you go with the revision goggles, you will have to peel back the fabric that covers the edges of the mesh and then cut away excess with a dremel tool or snippers. Be careful, it is easier to remove material than it is to put it back on
When you say not firing, what exactly do you mean by that? Have you considered its the battery? Also, what kind of connectors are you using? Sometimes the Tamiya connectors can become bent or messed up in a way that they are not making a solid contact.
Before doing anything inside of the gearbox, make sure you have adjusted the motor to the correct height, as that will help with some of the whine. If it is still doing it, the gun may just need to be shimmed and re-lubed.
Have you tried pushing on the bottom of the magazine as you fire? The magazines may be catching, but not fully engaging with the hop up unit, which would cause feeding issues. Also, what FPS was the gun shooting as the hard buckings are generally for about 450 FPS, and the soft are for under 450 I'...