Either way, I want to be able to format the text and use graphics in the email, so I want to be able to edit that email before it is sent.
FileMaker only sends out plain text emails, no graphics, no html formatting supported. To do those type of things from FileMaker currently requires using an email plug in of which there are several avaialable. You'd need to work with the plug in developer's info on how to use their product to figure out how to edit your outgoing emails.
Working with plain text emails, if you wil be entering all the text, you can use the send mail script step, but have it pause with the dialog open so that you can enter text. If you want to produce a message that combines text form the database with text that you enter/edit manually, you can use a set field step to put this data in a text field and bring up this text field when you want to send an email. After editing the text in this text field, a buton you click can perform a script that sends an email that includes the text from this text field.
The script that you have posted does not send email. It just sorts your recods into one of two different sort orders.
Oops! Uploaded the wrong screen shot. Here is the correct one.
This does what I would want it to do (close enough) for a single contact. Could I adapt the script to do this for an entire found set?
Much depends on the structure of your database and what layout is currently selected. It could be as simple as opening up the send mail step by double clicking it and changing the "current record" radio button to "multiple emails, one for each record in found set".