You have to recompile it...
There is no other way i know...
Get the source from here
Install a cross-compiler (for example CodeSourcery
start your folio with a kernel you like and get a working config (/proc/config.gz) and copy int into the kernel directory
gunzip it and then
make CROSS_COMPILE=arm-none-linux-eabi- ARCH=arm -j20
I dont know the name of the cross-compiler files.. Maybe they are a little bit different.
-j20 defines how many parallel compiling threads you like to have...
After that you'll have your compiled kernel @ /arch/arm/boot/zImage
And before compiling you are able to make some changes on the kernel..
But not on an compiled kernel..