Bill, The trace cut is shown under the manual . You are correct with the destinations but that trace between them needs to be separated anyway and this is a convenient way to do it. The AGC board is designed so that if you use a 3-pin right-angle header instead of the 2-pin shown, you can plug the board right in. Instead of bending the middle pin to meet the traces like the others do, drill a hole through to the ground plane on the underside just large enough to accept the diameter of the pin and bend the pin over to go through it. Scrape the coating off of the area around the pin there and solder it for an excellent ground return. Between the glue holding the new header to the board, the mechanical support of the new hole, and the three solder connections it becomes nice and sturdy. If you placed that connector carefully, the new board will plug right in with enough clearance to the other parts. Bring over your twisted pair from the volume control (or the plug), and your +5 volts (like the green wire from Raduino pin 3 and decide how you would like to select your AGC release timing.
Otherwise, bring those two coaxial cable center conductors to their respective "In" and "out" holes, their shields to the center hole between, and jumper between points #1 and #2 as shown.
My best advice is to take your time. Plan a lot, Work slowly. You want to make the experience last, right? Like taking a vacation. A person doesn't want it to be over quickly!
73, Don
Don, ND6T