Actually, modding might seem easier than you think.
(To remove goblin babysnatchers, try removing the [BABYSNATCHER] tag from the entity_default file.)
doing this would remove invaders from Goblins completely (as far as I know. They'll still send traders, and if you piss off the traders, they might siege you. Also, this doesn't stop them from warring from you, because that's part of a different section of the entity_default txt file, so beware.
You can also make more civilizations with purposes of trading and such, but they won't be much different from each other as far as I was able to do.
Adding [PET] or [PET_EXOTIC] to any animal will make them trainable, with the latter being only trained by dungeon masters. Animals can be tamed if they're caged. Adding animals USUALLY is just a matter of copy and pasting entries in the raws and modifying them slightly, unless you need to make some sort of completely different creature, like a flying four legged tortoise with chitin, or a legless worm with twenty arms made of steel.
Craftable items currently pertain to a small amount of moddability, meaning you can only modify small craft things like instruments, toys, and the latter, along with larger objects like weapons and armors.
I'd also like to say, that, 40d is a WHOLE LOT MORE user friendly when it comes to modding, because DF2010 has all these new material rewrites with the new tokens, using things like hydrodynamic aeroqualities, or quantum physics, and string theory, so you'll need to either be a rocket scientist, or just fuck around with the raws a lot to understand them, especially if you're a new modder. In 40d, a lot of the stuff were just tokens, and some of them were able to be modified slightly more deeper with numbers and fancy names.
All in all, start with 40d before modding 2010.
And by the way, this is completely different and easier from normal programming.
If you want more modding info, you can just ask. We don't bite, I swear. (except for the feisty ones)