I Need Help With Certain Features

I need some help with how to go about doing these five things:

• Replacing vanilla models for all the swords and tools.
• Adding the ability to block, heavy attack, and light attack for weapons.
• Adding animations for walking in different directions (backpedal, strafe)
• Adding animations for the above mentioned attacks.
• Adding a stamina / energy system to attacks.

Just to be clear, I'm not looking for help with the models or animations, I'm looking for help exclusively with the procedures that allow these things to happen in-game. Once I'm able to do these things, the first version of my mod will be ready, with pretty much just that for its content so far.