That part will probably be pretty tricky because there isn't really any development for it, and almost certainly no source code to build the kernel yourself. Your best bet is to check out some other phones that use the same chipset that might have some development that you can kind of piggyback off of. These other phones would be similar: http://pdadb.net/index.php?m=pdamast...d=1&cpu=a21654
It looks like the Galaxy Y Plus (i9001) has a decent little development community. The guys there would probably be more helpful with figuring out stuff to do since it has a similar processor. Might try to befriend a kernel dev there and see if they could give you a hand.