I'm using Dell 5150 and i've got Dell TrueMobile working on that. Firstly i have to tell you that I'm running 2.4.25 kernel. If there is no kernel in /usr/src, that means u don't have kernel source installed.
I would suggest downloading kernel-2.4.25 or 2.4.26 source from www.kernel.org
and recompile the kernel. I got a web page explaining what i did to get it running (www.dfernando.com/dell_setup.html
). But those instructions are for Debian distro. U'll need to download pcmcia-cs, rpm package and install it.