It would indeed be good if some modders joined up and started writing a comprehensive tutorial on mod making. Possibly covering both ArmA and OFP, I find ArmA more important though as it's newer and more likely that people will run into problems.
Sadly, I've never tried modding anything, most of the times I don't dare including mods in my missions because I want 100% working addons, most aren't. I know though, that there are a lot of guys on this forum into modding, probably at least some in the community have started working on a tutorial.