Used Pedro's instructions, and I don't doubt his expertise, but I couldn't get enough leverage to loosen the screws. The left duct was hindering me, so I modified my approach:
Removed left vent ass'y
Removed left duct.
Plenty of room to get my hand in there, plus one can use both hands from above and below. Maybe the difficulty is I'm left handed.
btw - as far as going under dashboards, back in the '60's we used to service car radios, so I'm no stranger to that, but not as agile as i used to be
