Pre-Order button and product list overlay

[ChariotsOfThyer]

Hi,

I have seen various mentions of being able to do this and seen the code for it but not for 1.7.2.

I would like to change the "Add to Cart" button text to Pre-Order is the product is out of stock but available for order. 

I would also like to be able to have an overlay on my product list, like the "Sale" one that says Out of Stock or Pre-order depending on the items status.

Thanks for your help in advance.

Ben