In the same boat here.
Latitude D420. Centrino Duo at 1.2ghz (since the 10.6.8 update though it's stuck at 800mhz). Broadcom 1390 wifi. 1.5gb of RAM. 80GB 1.8" HDD. No wifi, no ethernet, no USB. New EDP won't help because I don't have any way of getting it on the machine. Can't take the hard drive out because I don't have the right adapter to hook it up to USB.
I don't have any kind of kext editor loaded, and as I mentioned, no way of getting any new software or kexts on there. Any suggestions as to what I can do to at least get my wifi or USB working? I can post what my various plist files say if that will help.