Hi,
You'll have to edit :
- the file "cart" of the view "checkout" (for the order summary on the checkout) via the menu Display>Views.
- the file "invoice" of the view "order" (for the invoice) via the menu Display>Views
- the email "order creation notification" and "order status notification" for the order confirmation emails via the menu System>Emails.
For the views, you can swap around the blocks of code for each piece. It should be possible to do even without knowing coding, by looking a bit at the text in the files.
For the emails, it's the same. Note that you want to do that in the "preload" section of the email (at the bottom when you edit the email).