I think I can assist you here...
The current version of eCart is v4.5 (I think).
Using the checkout wizard, you can create an updateable shopping cart (add / subract / modify / delete ) All of the things that you would expect.
Regarding printing out orders, the combination of eCart and the Universal Email extension you will be able to get a very attractive "printable" receipt. This receipt can and should be mailed to the customer, and can be either CC'd or Bcc'd to anyone you wish.
I hope I answered your question.