Custom Virtuemart work in Joomla

Welcome coders, I need some changes in Virtuemart: - Enable correct Checkout with PayPal (it works, but the order is incorrect) - Enable to send Invoices with Back-End to clients (I can buy Extensions) - Add "Other bought this product also bought this" to Check-Out - Make sure, to get the shop working with secure socket layer (https) (prior in Check-Out) - minor styling fixes (like Alignment and position of registration-page and Check-Out) NOTE: Only Experts with experiences please. The website is running on Joomla 1.5.x and Virtuemart 1.1.x