Modify simpleinvoices to add a new data column to the products listing

I have an installation of the [login to view URL] software hosted on [login to view URL] I wish to change the way the products page handles our products. Currently the "Name" field in the products is the only data for both customers and office staff. I want to modify the this by adding a new "Description" field to the products page. So I can put in the products name for office users in the "Name" field, and have a specific customer description show up inside the invoices for that product. Screen shot attached showing sample data of the current working. WHAT I WANT 1) The products page to have one extra data column called "Description", which I can modify using the existing "products manage page" 2) Modify so the columns in products now read, "Actions, Name, Description, Unit Price, Enabled" 3) Modify so "Name" column sorts the data both numerically and alphabetically 4) Modify so the new "Description" field" is only seen by customers in the final invoice generation and output (e.g. PDF). 5) Modify so the office staff can see the "Name" field in the invoice creation drop downs and inside the products pages as they do currently. Office staff would only see the "Description" field in the final outputted invoice or the products page. Sample data for new system: Name - "1 - 5"x7" student ($10)" Description - "5"x7" photograph that comes in a folder" Name - "2 - 5"x7" standard ($12)" Description - "5"x7" photograph that comes in a folder" - I wish for a list of files modified and approximate line numbers. As well as the code changes to be clearly marked upon completion. - I wish for you to ensure all functionality as it exists right now is working correctly afterwards, i.e. you have seamlessly integrated the changes - I wish for you actually input the new system data based on my sample data. I will do a final clean up of the new "Description" text after you input the basic formatting so do not worry about being to specific and asking me, just your best guess will do.