504? IEP?

I've learned a little about it, but need to learn more. Last year was quite the struggle with David, and I don't think it's going to get better anytime soon. My understanding is that he doesn't qualify for and IEP. The medication just wasn't enough anymore - we didn't see much difference - so I'm trying to gear myself up for the new school year. Honestly, if he's not getting any work done at school (and it's getting sent home for him to do), I would rather homeschool him. For those that don't know, he's been diagnosed with ADD for 3 years now - he's 8.

I'm having a hard time understanding the difference between an IEP and 504, other than an IEP seems to offer and guarantee more. The best that I can understand is that an IEP expects and improvement in performance. While the 504 is just modifications in place. But I'm not exactly sure that that is correct. I've been reading books, asking questions, and not getting very far. One group just talked about getting a different diagnosis when I posted a question. His teacher didn't want to start the process last year (felt it was too late in the school year). Tomorrow is "back to school night" when we find out about teacher assignments, and the teachers are there to meet the students. I plan to ask questions of the teacher and principal then, but I feel like I'm going in blind.

Last year was much better than the year before (his 1st grade teacher hated him, I swear!). But we still struggled to get to finish his work. Any of it. He's been identified as gifted, and was finishing less than his Kindergartner brother.

I can't blame school - he's like this every day, for every one. The only difference with homeschool is that I would be able to control the amount of work required for him. But he loves being with his friends at school. And I'm not sure I'm ready to take on that responsibility yet, either. I've been barely keeping up with the basics lately. If I feel I need to, I'll do it. I just know it'll take a lot of work from me to get him to succeed.

Anyhow, I know I'm rambling. Any advice for talking to the school? Starting the process of getting a 504?