OS Commerce - update

I need someone to a) troubleshoot our OS Commerceshop (happened while we were trying to update files) Errors: "Warning: main(includes/functions/[login to view URL]): failed to open stream: No such file or directory in /home/stealth/public_html/eshop/includes/[login to view URL] on line 31 Fatal error: main(): Failed opening required 'includes/functions/[login to view URL]' (include_path='.:/usr/lib/php:/usr/local/lib/php') in /home/stealth/public_html/eshop/includes/[login to view URL] on line 31" b) install the following features: - allow users to download software they have purchased right after payment/payment verification (Download_Controller?) - install link exchange feature (Link Share Exchange) - install Live Support (LiveSupport_v12e) - install URL rewrite (to allow product names in links instead of the current settings) - any other useful feature that allows easy Search engine spidering/recognition