Magento Update To The Latest Version Needed

I am looking for someone with experience in Magento Ecommerce to update Magento. We have 6-7 Magento sites installed and so we want them upgraded to the latest version as well as updating all security updates both minor and major. Our sites have max 80 products in it at the moment but there is a part on the site that is probably done by custom magento core code which needs to be backed up incase something goes wrong. The freelancer who takes this project must be very familiar with Magento and must know how to properly update the site including making a back up just incase something does goes wrong when updating. We want this project to be done very soon.