Thumbnail and font size

Hi all
Hope you can help
I’m stuck on this…can’t find a solution
I need the thumbnail size of my shop images to be about 1/2 what they currently display at – preferably aroun 100 x 100 pixels.

Also the font needs to be smaller and the buy button gone (buy buttons are on the individual product pages so don’t need to be here too) any ideas? Also the row to display 5 columns/products

example below of how (wrong) it looks
http://www.soulstacks.com/shop/

anyone able to help?

thanks

http://wordpress.org/extend/plugins/woocommerce/