Oscommerce Work/Set Up

First item needed to be done if it is possible is to create a % discount for a manufacturer. I have manufacturers that offer a discount/sale at times and I would like to list it per manufacturer. I do have a old 2003 OSCdox 2nd item would be to set up a new Oscommerce type site. Install, set up Database and a few changes and alterations I am leading towards Cre because of their SEO addition. If i remember it changes the complicated web site address code to something simple that search engines can key into. Unfortunately business has about died so probably the lowest bidder with the best rating will get the job. I have altered the original OSCdox install about 50 times with little changes so there will be more work coming.