Magento Upgrade 1.5.1.0 to 1.6.1.0

Looking for expert for updating a Magento multistore webshop. Please only react if you and your team have the skills to do complex Magento solutions. This is the issue. We tried to do update from 1.5.1.0 to 1.6.1 ourselves through magentoconnect, however we encountered several difficulties and decided to go back to the 1.5.1 solution. It might be possible that some parts are still 1.6 however. We're ready to introduce a new webshop with new template through our Maegnto multistore install but before that we would like to upgrade to the latest version. We have way more work to do for skilled developers but let's start with the update. The project - Upgrade Magento Multistore from 1.5.1.0 to 1.6.1.0 (always first do offline test and you're responsible for backups) - You are only allowed to have our websites offlinefor the update between 00:15 and 07:45 CET (GMT+1) - After update check all critical issues (layout of product pages / layout of contact pages / log in account / cart / checkout) of the webshops to see if changes are needed in the template (we now have 2 different templates) ore installed updates and make changes For your information - We have the following extensions installed. * RicoNeitzel_VertNav * Flagbit_ChangeAttributeSet * AsiaConnect_FreeCMS * magento_easy_lightbox * Tangkoko_CmsSearch * BankPayment * Mymonki_Ship2pay * Frontend_Links_Manager * CashOnDelivery * Mxperts_Invoice * Mxperts_NoRegion * Auctionmaid_Matrxrate * Fooman_GoogleAnalyticsPlus * magento_easy_tabs * Ideal_Basic * BankPayment When done succesfull we directly have some more projects available. Feel free to contact me with any questions or remarks.