We are looking to add a series of yes/no radio button questions. Ideally we would like to adjust the content in the email based on what they selected in the survey (if yes, then show this). Are we able to place in If / then conditionals within the email content body like this?
Unfortunately there is no way to add conditional content to a message with the standard email editor.
However, you might be able to use custom scripting to accomplish this. You would have to start with the sgapiEmailSend function, and then add several sgapiSetHTMLEmail to cover each of the radio button questions that you have created.
A lower tech alternative might be to set up several SEND EMAIL actions at the end of your survey. You could then use logic to determine which email message is sent.