Adding mySQL table columns for posts? XML_RPC to mySQL interaction?

I’ve been reading through the code for the last few days now, tried a few hacks to test things out and see how everything interacts, and I’m still not quite there yet.

Here’s what I’m shooting for. I bounce around a lot and want to pop two more columns in the wp_posts table on the database, one for a GPS x-coord and the second for a y-coord, which will offer me some versatility in sending that data to Google Maps et al, to return a map of where I’m currently at.

In hopes of saving a little time, does anyone know how feasible a change to the database structure is on the WP side of things? How many (and which) functions or chunks of code am I looking at altering?

Things seem to have been put together pretty smoothly, and I would think it’s a fairly straightforward hack, it’s just a matter of me humanly sorting through everything to figure out what information is being passed where, by what, and when etc. Several thousand lines of code spread over 100 php files is quite the haystack to sort through though and I’d appreciate any leads.

On that same note, is anyone fluent with the XML-RPC API? Or exactly how it interacts with mySQL? If I were to get the hack working for webposts, what am I looking at to add the same SQL table inputs to the API?