501138 Upgrade X-cart 4.3.2 to 4.4.3

Hi Everyone, Need professional upgrade from X-cart 4.3.2 to 4.4.3 including design re-implementation. Must work on all browsers and tests must be made. my current design is at [login to view URL] I have part upgraded my site to 4.4.0 on a test server but struggling upgrading it to 4.4.3 - Then I need to implement the modules myself to save money. Perhaps a little help here and there. A couple of areas need a tiny tweak in appearance as checkout pages don't look very tidy now. If easier we could do the upgrade at the end, as before I go live, I really need to sync all the customer and order data from old 4.3.2 store. Please give me suggestions of best way to upgrade process if I wish to keep all customer and order data up to date before going live. Need this completing within 2 weeks max. All the best Anthony