I'm not a slacker, but your kernel source code is in:
/usr/src/linux-<version number>
and there should be a link
/usr/src/linux
that points to the source code directory.
You might want to rename your old kernel and edit your bootloader to reflect this if your present kernel's name is bzImage
To configure your kernel for compiling as root:
cd /usr/src/linux
make menuconfig
This is where you configure modules, etc. Save your config when exiting
Compile your kernel (working directory is either /usr/src/linux or the actual directory of the source by commanding:
make dep && make clean bzImage modules modules_install
Then copy your new kernel:
cp /usr/src/linux/arch/i386/boot/bzImage /boot
Edit your bootloader, run /sbin/lilo if you use lilo, etc.
The Linux Kernel HOWTO
HTH