The SKU is normally something that is associated with the items in the order details table (detail) not the order (master). You should be fine in going about the email setup like you have described, you can use the form field values directly in the email message. When you are on the body tab and choose to edit with DW you will have the form fields available from the bindings tab.
The values that these form elements are set to come from the recordset. You can reference these values directly also from the bindings tab. If you expand the recordset and drag a particular column into the body of the email message you will see that columns value for the current record in the email. If you have not tried this already you should just give it a go, I think it will be much more clear for you when you go through it and see the end result even if it is just a test.