I finally got my cable and screen from that seller on taobao. I don't think the screen itself is an official GBA SP backlit screen, but rather a cheap reproduction. Why? It has a terribly low refresh rate (ghosting) and I can practically see the lines scanning. But, I've never seen an ags-101 before, so I have no reference anyway. Regardless, I may try to source an ags-101 anyway, and try that out.
Anyway, as far I can tell, the (40-pin) cable is just merely an extension for the LCD with an added wire to power the backlight. The reason for this, for those that don't know, is that the standard gba screen, the cable is on the top, and for the GBA SP screen the cable originates out of the bottom of the screen.
(I tried to get as clear of a picture as possible, but my only camera is my iphone)
Installation was fairly straightforward after following the pdf install guide. I translated it via google translate, but to be honest, the pictures did a pretty good job anyway. This mod will require you to shave away some plastic from the inside of the front faceplate. I just used a dremel, but I'm sure a hobby knife would work just fine.
Me testing the screen:
And all put together:
I'm satisfied with how it looks and works, but as I said, perhaps I'll cannibalize an ags-101 in the future.