I have console with broken LAN. After plugging a cable green and yellow leds aren't blinking. Network isn't visible of course. The rest is fine (other consoles works properly).

What can I do instead of replacing mobo? I have dead mobo, I could desolder LAN and replace it, but is there chance that it will fix?

Read this thread. You may want to PM Perplexer and ask him. Looks like it could be done.

I saw a thread here a long time ago about adding a wireless adapter to the Xbox. You soldered it into the MB. You may search for that too.

Thanks! I am in contact with Perplexer, he will send me spare ICS chip.

ICS chip was replaced, and actually LAN is working properly