Need help regarding categories in Open Cart 1.5

Hello,

I want to make some changes to Open Cart 1.5 and I am not sure how. I know some PHP and JavaScript but I could use some assistance, so simply I am merely asking for guidance on which files would I have to edit to make some of the below changes below possible.

Remove multiple currency choices, only allow US ($)
Remove the (#) from the categories tabs that displays how many products the particular category has
I want to see the images for categories instead of a list, similar to how you breakdown categories in 1.4
Remove "Refine Search"
Have a "Show All" option from filtering the product list