Here's Embedded linux from scratch, in 40 minutes. Here are some slightly longer training courses. All free and online. They're licensed under "Creative Commons", and I know you hate that shit, let us know if thats why you haven't bothered.
OK, enough of that, I do have these skills, but they're not needed. The rtl8181 project (on sourceforge) has source for a 2MB version of linux running an 802.11 AP. (There is new code released under the GPL for the rtl8186 "11g" AP-on-a-chip, too.)
The nice thing is that both the rtl818x and the Broadcom BCM4712LKFB are based on a 'mips4c' core, basically a MIPS32 CPU with the associated "mips standard" MMU. Therefore, with small exceptions of code side due to differences in the populated board (say, the ethernet chip) or software functions, and trivial differences for the kernel (CPUID) and bootloader, the same code could run on either part.
So, its entirely possible with slight twists to get a 2MB flash/8MB ram footprint linux codebase for this machine, but this leaves precious little memory and flash for anything "extra", which is what the guys at OpenWRT (etc) love to do.