Yes, you can apply formatting and include hyperlinks within the body of the email. Learn more in Formatting Text in Campaign Notifications.
You cannot change the email header. The header includes an Emtrain branded image and the user’s first & last name, which come from the First Name and Last Name fields in their user profile.
If an employee has a preferred first name and you haven’t yet set it up in their user profile, enter that name in the First Name field of their user profile, then add a Custom Field such as “Legal First Name” to your user roster, where you can enter their legal first name.