So, Minecraft.

[DeeBye]

If you have a steady source of wheat you have a good start for food.

You can mill up the wheat in a pinch and make bread out of it, but generally that is an inefficient use for it. Go out and make a fenced in pen and if you are holding wheat you can lure a bunch of animals into the pen. After they are in there you can use the wheat on two of the same type of animals to instigate reproduction between them. Once you've got this set up you should be able to have a consistent source of meat.

Is it advisable to do all this wheat/animal farming inside my little safe dirthouse, or can I do some of it outdoors?

There's creepers out there and they go boom.