What's the heater/air box next to the blower motor? It's closer to the center of the car, right next to the blower motor on the passenger side.

I cut the plastic of it, thinking it would help me install my headers... I will replace it eventually, but I was wondering what that box is and if it will affect my heat or AC?

Also I see the bolts on the top and close to the firewall, is that all I need to remove to replace it?

 

It's the evaporator housing.

The A/C evaporator, which is the piece that actually gets cold, is inside it. Air blows through it before coming out the dash etc. vents.

Won't work right with a hole in it.

There are a total of about 7 bolts that hold it in. They are all relatively large; 10mm head if memory serves, maybe larger. The itty bitty screws all around the top don't have to come out, shouldn't be disturbed in fact. A couple of the hardwares are inside the cabin across the bottom, under the top edge of the carpet, you'll have to peel it back. The whole thing will lift right out of there. In fact if your A/C still has its charge and you don't want to disturb it, you can literally lift the compressor, condenser, and evaporator assy up out of there as a unit, without discharging it, if you pull the radiator out of the way.