Overriding Vanilia Properties / Code

Hello,

As most of you knows vanilia MC has some disadvantages, and when you try to butt-in with your mod you may get stuck on some things.

Let's say I've got more (using Forge) EnumToolMaterials, and i want to implement them in game. Yeah - thats VERY easy, but there is one problem - i've got to obey some rules of vanilia code. We got Wood->Stone->Iron in vanilia, and i want to put, let's say: Copper, Steel, and Bronze between them.

If we follow real life hardness it should be: Wood->Stone->Copper->Bronze->Iron->Steel, and i've done it so... BUT!

But... i want for example change Diamond's (and others) Hardness, which is 12.0F, or its Durability (1561) to lower - I dunno how to do it without butting-in into Vanilia Code (and I don't want to). How can I use forge to override properties / vanilia code in minecarft?

Second question (actually the same) - how can I use this overrides to ,,replace" IronBlock with MyIronBlock (or just override IronBlock properties)

ex.

When in mod you got:

public static final Block OreIron = new MyOre(1001, 0, Material.rock).setHardness(2.0F).setBlockName("IronOre");

and in vanilia you got ,,something", I want minecarft to use MY OreIron, not the oryginal one (it needs to be done by minecraft itself - some of plugins - not mine -  use IronBlock ID and I want this ID be automatically changed into my ID (and other properties as well).

Sorry - I just write much   - Hopefully everything is clear

Thanks for help,

Ernio