Oscommerce credit card integration

Hi! I run successfull website and have recently built a store. Everything is set up ok, but, the small but big but is. I go through the order process with [login to view URL] and when click on finalize order, and when come back to oscommerce with the following message: "There has been an error processing your credit card. Please try again." It is the [login to view URL] script. Anyhow. I need this to be fixed as well as a i need help to install the support for downloadable products (md 5 hash) with [login to view URL] I sell both downloadable and tangible products. As well i use paypal as second processor. They need to be setup so they work with both physical and tangible goods, so far no problem what i have seen. But i need a check on this as well. I also would find it positive if the following language modules could be installed as option: German and spanish. I estimate project to be worth 100 dollars. I need it done swift and without any hassle. The payment will be just as swift through western union if that is ok with you!