How hard is it to mod minecraft?

I'm an AP computer science student who is pretty good. We haven't done much with graphics but are passed interfaces and inheritance (obviously first year stuff). We will be creating an android app for a final project to give you a sense of difficulty (I don't know if that's much easier than minecraft or what). Should I learn all the graphics stuff before starting mods?

Thanks

Added (1). I do mean make the mod.

Not at all. Just look up youtube walkthroughs and you can download and install mods within an hour

Do you mean making or using mods?

Modding Minecraft is made easier using tools like modloader and forge. These give you the ability to add things to the game in an easier fashion. There are tutorials on the internet that will give you tips on how to use these, but I have heard that it is not hard to put together a basic mod quickly. I'm not a modder myself, but I believe there's no need for graphics skills aside from making textures for new blocks and items you may wish to implement.