I can't help much but the "he/she" thing is sorta annoying so I'll tell you how to tell if its a boy of girl
Boy
1. Long (I mean, real long) claws on the front paws.
2. A fat tail and it is longer than a female's tail.
3. A slight concaved curve on the bottom part of the shell.
4. You might notice more aggressive tendencies.
5. The cloaca (opening) is closer to the tip of the tail than the body.
Girl
1. Shorter claws than a male's claws.
2. A shorter, thinner tail.
3. Flatter plastron (bottom of the shell).
4. females tend to be larger than males.
5. The cloaca (opening) on the tail is closer to the body than the tip of the tail.
thus your lil (BIG) turtle might be female, but I have to see it to make sure... maybe some1 else can help you with the rest

grim, if I had a shell, I would have to sleep on my belly.....
Call me 'Hero Flame'