on mine there is just 2 screws on the bottom, and one on top. then you just have to pull it out carefully.
if it's to stop drafts, you could just stuff something all around the gap. the AC need the air around it to circulate when working, it sucks air from the top vents on the roof to the sides of the AC, and out the back, so if you add insulation, be sure not to block that flow.
2011 Swift SLX 154bh /2012 Rav4 V6 with airbags & 15k btu transmission cooler.
km counter: 1700