I have an item with two NBT tags. I want Minecraft to look at what is in the crafting table and tweak the NBT tags based on that in the output. Someone suggested and IRecipe class. How would I do this or is there a tutorial?

How do I register it?

GameRegistry#registerRecipe(IRecipe) is what you want.

And then how would I a) detect if the items in the crafting table are the ones I want and b) How would I tweak the NBT of that item based on the other items in the crafting table?

Override getCraftingResult. That gives you all the items in the crafting grid and you return the stack that those items will craft.

 

Example:

@Override
public ItemStack getCraftingResult(InventoryCrafting var1) {
ItemStack result = super.getCraftingResult(var1); // The itemstackthat this recipe creates

       // Add your nbt data to the itemstack

return result; // Return the itemstack
}

Is the recipe handler supposed to extend another class? Right now it just implements IRecipe and there aren't any super methods

Min extends ShapedOreRecipe which implements IRecipe.