customization an Online Shopify Store

Our Goal is to have a Shopify ECommerce (which we have already set up to sync with a RMS point of sale with RMSIFY app) I actually started to work on the site already and am now uploading page like about us etc. What I need help with is getting the shop pages to look the way we want them to. This will take some css and php changes. We have a tight deadline and will only want people applying if they can do the job quickly. We actually have two stores that will need a job like this also if we like your work done on this one. In Shopify I need a page template created for a category. Example: Road Bikes. I need one page per category. You will see the category list in the site as I have it already synced with the point of sale, the site is now on Local host. One these pages I somehow need the images all to end up being the same size even though they are different sizes in his pos. Not sure how this can happen. This is my requirement I need the product images to be the same size and create a page for every category that is synced with the pos such as Road Bikes, Mountain Bikes etc. The pages would have a 3 image slider that shows up on all of the category pages. It can be a 3 image simple flex slider. Not all of the product images in the pos are the same size but I need them to show on the web site as the same box size. Not sure how this can happen. You will need to educate me on what can or can't be done. Thanks Biswa