Disable oscommerce checkout

Hi, I want to disable my oscommerce checkout page (so nobody can purchase) as there is some maintainance work i need to do. Also, i need a note on the shopping cart page. On [login to view URL] - i need a message in red underneath "Your Basket Contains:" "This website is currently unavailable while we perform some maintainance - you will not be able to purchase at this time - we will be back soon" On [login to view URL] - i need this page disabled completely. Maybe redirect [login to view URL] to a custom error page stating - "This website is currently unavailable while we perform some maintainance - you will not be able to purchase at this time - we will be back soon" Also, you will need to tell me how to restore these pages to its original state. Need this done pretty quick - should should be quick experienced oscommerce developer.