As far as flying two quads on one radio, you can just buy a Spectrum (compatible) receiver for the 2nd quad and use ANY controller. There are lots of DSM2 compatible receivers out there. Here's one:
http://www.hobbyking.com/hobbyking/...2_4Ghz_Receiver_w_Failsafe_US_Warehouse_.html
It's $14. I wouldn't take on this modification job to save $50! And I don't actually think the receiver IS integrated on that controller, otherwise there wouldn't be input leads on it too.
As for the connections:
You connect the three control leads (brown, red and orange servo wires below on left) to the correct OUTPUT channels on the controller. Again, that will require you adapt to those mini-JST wires/connectors (and you'll have to know which side of the controller is INPUT, and which is OUTPUT.
Connect TWO wires from the power distribution (in this case, the controller) to the ESCs. Since they aren't control wires, any red and any black can go to any ESC. (see the red and black extending out of the left side below)
Then the three wires extending out the right side of each ESC connect to the three motor wires. Usually they are somewhat color coded, but the ones you chose seem to be all blue.
You cannot connect those three in a damaging way, so just solder them to the three motor wires and if any motor doesn't spin the direction it's supposed to, you reverse any two wires leading to that motor. Normally, a controller that is pre-configured for an 'X'-copter is expecting the opposing motors to spin the same direction, so you have one CW and one CCW in front, and in back, but reversed in back. If you think about it, this makes sense, because you have to be able to keep the quad in the air while rotating on its center axis (yaw) which can only happen if you slow one pair of motors turning one way, letting the other pair pull it around.
I recommend using shrink tubing when soldering the motor and ESC power leads. Feel free to shrink the black and red joins as soon as you're done -- you won't need to open those connections. But only reduce the tubing on one wire on each ESC/motor and leave the other two expanded but maybe held in place with electrical tape so you can easily swap them. Then when you get the rotation correct, shrink the remaining ones to finish the job. SunnySky motors generally do not come terminated, but have nice long wires, so you'd have to solder something even if you bought ESCs with 3.5mm bullets.
Set your controller in position, see how far those red and black wires on the controller and ESCs will extend and try to position the ESCs out on the arms (zip-tied down), then mount the motors and bring the wires to the ESC wires, cutting off the excess motor wire leaving a little slack. In other words, you want the ESCs as far from the controller as you can comfortably get them (as they emit RF noise) and no loops of spare wire out on the arms.
Now, which motors the controller expects to turn clockwise is going to be a puzzle and it matters because the controller will expect to throttle up one opposing pair to yaw left, and the other to yaw right. You may be able to find it on YouTube, or info on servicing the "Blade" quad you got this controller from, but then you'd still have to figure out which ESC connection on the board went to which corner of the Blade. If you can't find the information, just wire them as I suggested, and if yaw (rudder) is reversed, reverse that channel on the radio or reverse a pair of wires on all four motors.