Need direction for ecommerce

I am a designer, using photoshop and hard coding HTML 4.0 / CSS. Also a bit of javascript. I use a PC, WinXP, and have fleeting familiarity with MySQL and PHP (have never "written it" though). I have always built sites on unix-based servers, never windows based.

I want to expand my abilities and am seeking books and other resources to learn how to process forms (I know how to build them with html, but not how to make them function at the server level).

Also want to be able to develop e-commerce sites for people (maybe using OScommerce? OptionCart?). So, I am looking for direction and suggestions for books and online learning resources. I am pretty confused about the interrelation between catalogs, carts, gateways, merchant accounts. I want to create a streamlined process for my clients!

Can you tell me how you learned these skills? Thanks!!

I came to this forum because I wanted to get away from the first one. OptionCart seems to have some sort license purchasing requirement, and I don't really know it etc... So I would suggest the other one, thats how I started, but I'm waiting for the next release... in the meantime it would still be worth a look, and there are lots of contributions... knowing (learning) the first, will help you build the skills you're seeking.