Prestashop Expert - Upgrade, modules themes

We are looking for prestashop expert and who can finish our project in 24 hours. Running prestashop 1.4.11 and we need to update it to the latest version. Our theme should remain same on latest version , with our current modules. We also use one custom module of payment gateway . After completion test should be done properly on test server and after testing and checking you will need to move new orders and customers so that we can live our latest version . . Server - SFTP with ssh will be provide to work with.