help customizing shop

[robadooda]

would like to customize my shop in a few areas if anyone could possibly point me in the right direction::


1. Because my products need to have different postage costs if i would be able to add to the product update in admin a new field where you can enter the price of postage then this is taken into consideration when a customer checkouts. I also need the price of a second item with the same postage cost to be a set percent less. like the x & y postage contribution.

2. When a user goes to a categpry and they see the links for each of the sub-categorys if possible to have all the products within all the sub categorys listed below so if they want to view all they can or if they want to split them up via sub category then they can choose to do so.

I would be super appreciative of any help and advice anyone can give.

thanks in advance