Magento payment gateway

Our website www.gymequipmentdirect.com.au was accepting online orders and payments issue free; however, we now have a new merchant for our payment gateway/online payments and have purchased a suitable plug in. We need a Magento expert to complete the set up so that we can resume accepting online orders and payments ASAP. Note we use Amazon Web Services as our cloud computing platform so I guess experience with AWS would be a big help.