Is it possible to allow only members to view the products?

> Is it possible to allow only members to view the website?
> Can we force users to log in or register before they view
> the products and prices?

Yes, this is possible.
Just specify Membership level for category you want to hide in
"Control panel" -> "Category" -> "Modify".
Your visitors will be able to see this category and products inside only after login.

It'll be a good idea to place login box in the middle of your home page and tell people they have to register/login to see the products.