Opencart - Change the defaulty shopping cart icon

Im looking for an opencart expert that can help me with a small project at this stage, with possibly more work to come. Today I would like to change the default shopping cart icon at the top right in open cart. I would like to use a JPG or PNG image with a green icon on top that will show a number when items are added to the carts, the same system as what is currently used, but just put the image below, and change the shape of the green dot.. see image.. I would like to upload it myself, so you edit the file and I upload it. See the image for example.. I can supply the images