A client wants me to quote on creating a shipping module, and although I've had a fair amount of experience customizing ZC (both look/feel and functionality), I'm not sure where to start. Basically it's an option to ship with a trucking company that bases rates on a combination of weight and zip code, shouldn't be too hairy. But how do you create a contrib? The documentation I've found is pretty sketchy/nonexistent. Anyone able to give me some starting advice? Any thoughts on how long this development would take? Thanks loads!