Scratches can either make the plastic shiner (by carving a smooth reflective channel into the material) or duller (by carving a rougher surface into a shiny plastic).
If the scratches are duller then the entire surface (rougher) you can attempt to lower the sheen of the entire panel by scrubbing with an abrasive medium such as a Mr. Clean Magic Eraser. The problem, though, is that it is very hard to get an even finish and that one panel will be noticeably less shiny then the others.
If the scratches are shinier then the surface then you can lightly polish the entire panel with a fine abrasive, but again, you are increasing the shine level of the entire panel and it is very hard to get an even finish.
The good news is that replacing panels like that is usually fairly inexpensive and its normally just a couple snap fittings holding in place.