Starting from scratch with an excel file?

I've got a new project coming up for a wholesaler but a huge question is looming.... This wholesaler has hundreds of users and thousands of products that are updated every day with quantities and pricing and are exported via an Excel file (which they will want the site to be updated daily with).

My main question is will I have to manually setup each product the first time, or is there a way I can import that excel file which contains products name, pricing, quantity on hand, manufacturer, part number, and of course the clients usernames and passwords first?

And a secondary question would be how easily can this be done/updated daily??!!

Sorry one other thing... its not a big deal to setup the cart to not accept payment is it? We simply need someone to login using their username and password that we have previously setup and when they submit the order we just need to get the email with the order details.
Thanks again