In the awkwardtv.org forums (and wiki) there's a bunch of info on getting AFP going. The problem is, ever since 1.0, Apple has made a bunch of changes making it really hard for some to get it going. For some it's a breeze and for others, following the same exact directions, it doesn't work. I have an original 1.0 ATV upgraded through the versions and I've never been able to get AFP working. In version 1.1 I was able to get SMB working but that has now broken in my latest setup due to using Leopard on my media server (Sharity Light is incompatible and I can't get the built-in SMB working).
Some of the issues have been Apple has yanked out the required AFP pieces and lately there's issues with the Kerberos components (different md5 checksum). Albeit this may be because of the Patchstick I used (atv4windows) installing a different version.
You definitely need an original 1.0 Recovery image. Check torrents for that one. I've also heard there's some pickiness on 10.4.9 and/or 10.4.10 Update disk you use. Once you get these together then go up to the forums at awkwardtv.org and follow the different posts up there. There's so many of them I can't recommend just one. Good luck!