2003 Chevrolet Venture A/C front expansion valve

I am reasonable competent at auto repair... I've even replaced a transmission once and a head-gasket once. So I can do most jobs. Currently, I am overhauling the A/C system on a 2003 Chevy Venture with rear unit, which quit last summer. I've replaced the compressor, the condenser, the accumulator/drier. I am now working on the expansion valves (both front and rear). I'm 98% sure the FRONT expansion valve is mounted on the front evaporator under the dash. Problem: I cannot remove the last panel to access the front evaporator. I've dissembled the underside of the dash down to the heater core, which I removed. But the evaporator (which I can see and feel through a few small openings now), is behind one last panel that I cannot figure out how to get off. I'm beginning to fear the entire box, including the actuator motors and flaps, etc, needs to come off... but I cannot see how to do that either. I just want to replace the expansion valve. Any advice?