1997 Clean out AC cold air plenum

[HalTbird]

I suspect my AC cold air plenum.....the chamber where the AC evaporator is located, has become the resting place of a lot of dry leaf, tree debris. How do I access it to have a look and vaccum it clean? I notice that under windshield there's a long metal strip that has vent openings that's probably the vent openings for the AC. Looks like the windshield wipers may have to be removed. There's some screws that holds down this metal strip. Anythink to know about venturing under this metal strip in search of the AC cold air plenum? Thanks!