Just buy a proper LCD to modify, it's not worth the time & effort for such a small lcd. You can find 5" psone LCD for under $50, alot of people have used those to modify.
Whats that got to do with it? Most non-PC specific displays just need the controller to get them to work, its nothign to do with a processor
Processor/controller its the same flaming thing but the gba screen hasn't got one,The lcd is controlled by the main processor of the actual gba.