Hello, the problem you have is going to be difficult to over come at best. I am going to post the ways to open the truck at the end of this post. But, if you have a problem that keeps the trunk from opening in the normal ways and want to access it by going in through the back seat, the you will need to remove the seat cushion and the seat back to get into the trunk as the fold down seat control is also located in the trunk so you can't even fold the seats down with the trunk closed. If that is the case and you need help removing the rear seat drop me a note and I will get you some instructions for doing so. But the only other ways to open the trunk are posted below. The trunk release button is item "K" in the picture of the dash at the bottom of post. Thanks
Rear Compartment Lid Release
The rear compartment lid can be released in one of three ways:
To operate rear compartment lid with the rear compartment lid release switch or with the rear compartment release button on the key fob, the gear selector may be in any position, but vehicle speed must equal 0 for the rear compartment lid to release.
When the rear compartment lid release switch is pushed, the rear compartment lid release signal circuit to the body control module (BCM) is grounded. BCM then grounds the coil side of the trunk release relay through the trunk release relay control circuit. With this voltage is applied to the rear compartment lid release actuator, opening the rear compartment.
The main components of your instrument panel are the following: