AkaSigFreak

I had plans to install a new JL Audio Power PowerWedge+ in my 2014 E350. I ordered the subwoofer, amp install kit, and the remote knob. I reviewed all of the posts in this forum pertaining to amp installs and tapping into the source signals. I think I located the amp under the rear deck and the wires, but the harness is so tight and there is absolutely no slack in the wires. I'm nervous that I will damage something. I have a friend who owns a high-end audio shop but he usually likes to sell the complete package (Components, Parts and Labor), so I hate asking him to install it for me. I'm so frustrated because obtaining the source signal from the trunk is the only thing I can't do myself. I'm sure if I spent more time in the trunk I could figure it out, but I have herniated disks in my neck and back and I'm still recovering from 3 shoulder surgeries so I am physically unable to fit into tight spaces.
Does anyone have any pics or details as to where I can easily tap into the subwoofer cables?