1)kernel source is under /usr/src/linux. if u have no source under /usr/src. then u need install from cd.
2)all compiled kernel module is under /lib/modules/2.4.xx/kernel/...
3)if u know the name of module and u find that module under the 2) dir. then u can use modprobe to load it. see 'man modprobe' to know how to do.