Amazon Product Data File Template Revised for Existing Listings

We are currently selling both FBA and seller filled listings on Amazon. We need a new updated excel template created for those items so we can make changes in descriptions, quantities, pricing etc. in bulk and upload the template through seller central. I know it's one thing to put these items into a template but we want someone who is highly familiar with the correct template, nodes, browsing trees, etc. I can either provide the various original Amazon upload templates or I'm guessing I can download something from our seller account of all active items with some guidance. We are in a rush for this updated template. If satisfactory, we have a second unrelated account where we need the same thing done.