@charaznabl39130 "screen dying and causing my battery to drain faster?" most likely not. this sounds strictly like a bad back-light. You do want to remove the screen. Clean the connector with some isopropyl alcohol and cotton tip applicator. Check the ribbon cable for tears, corrosion or frayed ends. Check the button with a multimeter in ohm mode, to see if you have continuity when on and no continuity when off.
It also depends on how dark is dark. It is possible that the complete backlight has failed. Let us know the exact model number for your GBA SP and post some good pictures of your board, the ribbon cable and connector. That way we can see what you see. [guide|21499]