How to get to my A/C evaporator

Hi everybody. I need to do an overhaul on my A/C system(because of a leak) and somebody told me that it was leaking at the evaporator core under the dashboard. Now I started taking apart the black box under the dash. I took off the very lower cover on the bottom and slid it down which revealed my heater core. Now I assume that the evaporator is above the heater core in the next compartment of the black box. But I do not know how to get to it. Please help

If I remember correctly, you have to remove the dash to access the evaporator core.

I believe that the evaporator is located on the passenger side of the truck, but it is mounted on the fire wall in the engine compartment. It should have a sticker on top of it telling you that it only accepts R-134a. It also has aluminum hosed running into it. Very easy to fine. I am not sure about removing all of that black box under your dash.