Apple offers a free, open source firewire driver (originally created by Zayante). This driver is way overkill for embedded projects but you might get some ideas from it for a scaled down, embeddable driver. The driver is designed to be os-portable, but you really have some serious work ahead if you want to port it to any os other than the included samples. It comes with a huge amount of documentation which may help you figure things out.
In conjunction with the apple driver, you might want to pick up a copy of "Firewire System Architecture" by Don Anderson. This book is short on implementation clues, but it's a fairly comprehensive "plain text" description of 1394 details that you won't find in the 1394 spec.