[RangerDown]

Why don't I lead you to a couple of files from the source that might be of use to you:

zone/eq_packet_structs.h
? zone/eq_opcodes.h ? <--- not sure if this is the right name but something like that

I get the feeling that this is the extent of the "typed up documentation" you suspect exists. That, and a few discussion boards on the net like Hackerquest. The source code exists at SourceForge as the project name "eqemulator". In the case of network packets, with that stuff changing every other patch so it's futile to try and keep up separate documentation about it. In cases like these, the code simply has to be the authoritative source.

I've found the current crop of devs to be pretty open when it comes to asking questions about the inner workings of the system. They don't always have time to be bothered, but if you're motivated to help them they'll be motivated to help you.