Just pull the carpeted panel off on the passenger side. I don't think you need to pull the radio. The valves are metal cubes with wires and hoses attached. They are mounted on a metal strip. I just ran a continuity test on each one to weed out the bad ones.

__________________
1985 380SE Blue/Blue - 230,000 miles
2012 Subaru Forester 5-speed
2005 Toyota Sienna
2004 Chrysler Sebring convertible
1999 Toyota Tacoma