Expansion valve change on a 420 SEL

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Good evening out there in Benzville! Has anyone changed an expansion valve on a 1990 420SEL? I'm leery of having to pull the two airbags if thats needed to complete the job. Can you access the valve from under the drivers side dash without having to pull the steering wheel? I assume if the evaporator is bad the whole dash has to be removed. I'm not picking up any refrigerant coming from the evap. drain but I am around the accel pedal area. If I get in there and it looks like the evap. is bad too, will I need special tools to remove it? I'm hoping it's just the expansion valve. I know the drier needs to be changed too, but should I replace the pressure switch also? Thank you, in advance, for taking the time to answer my questions!!