I bought one of these for my GBA. It is relatively easy to install if you are happy soldering (get a fine tipped soldering iron as 2 wires need to be soldered onto the motherboard of the GBA), however there is a process of sticking an anti-glare film onto the LCD screen which is very difficult to keep dust free. Also the slightest particle anywhere near the LCD screen and the cases own plastic cover show up really bad.
Given the choice I would not buy this product again, it allows the GBA to be used in the dark but you loose quite abit of quality in the daylight.
For the price just part chopping your GBA for a GB SP, which Im doing as soon as I remove the afterburner kit.