There are tons of tutorials out there that describe custom post types all over. HOWEVER, I have only found a couple very confusing ones that explain how to use custom post types with file inputs! Here's a simple and easily understandable way to use custom post types in Wordpress 3.0 *WITH* image uploads! For this example, I'll be creating a 'Portfolio' custom post type with a few text fields, 1 field for thumbnails and 3 fields for extra images!

Yesterday at work, I was having trouble passing multiple variables through the URL as a $_GET variable. If you're printing (print_r()) your variables and they are just coming out as strings of 'Array', I may just be able to help you out!