Standard Horizon Intrepid+ VHF case removal

[belizesailor]

I have an Intrepid+ VHF which I think just has a bit of moisture in the power/volume pot. I want to remove the exterior housing to check it out. I've removed the four screws on the rear corners of the housing and assume that the housing would then just slide off the chassis, but it wont budge. Don't want to break anything...anyone removed one of these housings before?

Thanks.

(I know Standard Horizon has a flat repair service, but it would cost me more to ship from here than the radio is worth...so might as well give it a shot).