Should I replace my built-in cutting board or etch it?

A glass cutting board was placed in a cut-out section of my kitchen countertop. I took it out to clean it and found that this buildup was between the glass and something that was adhered to the bottom. It wasn’t contact paper (I tried to replace it with contact paper, but it?s too thin and tears when I screw the bolts back that hold the glass in.) What can I do to make it look good again? The glass is clear, and you can see the top of the dishwasher underneath if I don’t put anything on it. Should I try to etch the glass to make it opaque? Or replace it (and where would I find a replacement?) Help! I’m trying to sell me house. Thanks!