WordPress Website Help

I have set up a WordPress Website selling Wedding Invitations. I have the products online and various pages but am scared stiff of attempting to put a payment system on the site. Also I would like some guidance on whether I should use posts or pages for my products. At the moment I have used posts but have been told that pages may have been better. In a nutshell I have started a WordPress site and I want someone to finish it for me. So if there are any WordPress geeks out there please help.