I've worked with only AC boxes.
It sucks.
The dash can be loosened and pried far enough to get clearance for box removal,
BUT I'm not sure how much I would want to pry on a 30+year old piece of plastic that's almost irreplaceable. Thus I would remove the dash.
And having to remove the AC lines ... I get shivers just at the memory.
Plus, splitting the box sucks. Make sure you remove all screws and clips. Pry gently and work around the box evenly and carefully.
This is not a job you'll want to do twice so do it the absolute best you can.
And,
who is amanda chaingete, looks like it could be the name of a S&M Porn Actress.
