Looks like you have six screws holding that panel in place. I'd pull those out and see if you get rear access. Some gauges are clip based and some are threaded nuts.
Fred & Denise (RVM157) New Mexico
2007 Excel Classic 30RSO & Coach House 272XL E450
2007 RAM 3500, Diesel, 6Spd Auto, SWD, 4x4, CC & LB