If you set the price of your product to zero dollars it will skip the payment screen.
If you have configured one of the shipping options that displays shipping methods to the user on the cart page then you could jsut configure one ship method and the cart will default to that ship method so the user doesnt have to select it. Addionally, if you configure one of the shipping options that dont display shipping methods to the user like shipping by order amount, product level ship costs or free shipping then the user will not be required to select a ship method during checkout.
To add static text to any of the checkout screens just open the ascx page you want to modify in your favorite editor and add the text to the page and save.
-Scott