Q1: My step isn't sending emails to the correct person. What's wrong?

You should confirm that the Contact who is receiving the e-mail ("To Specific Contact" on the Step record) has a valid email address on their Contact record. If you are dynamically identifying the Contact via Email To Contact Field, you need to confirm that all potential Contacts have valid email addresses. If the email address is empty on any Contact who is supposed to be emailed, the email is sent to Default Contact instead.

Q2: How can I edit a template for my email step?

If you aren't sure which template is being used for a specific Process, go to Administration > Processes > open desired Process > on the Steps subpage, open the E-mail step > look for Email Template > click the jump link next to the template name. You are directed to the Template's Message record, where you can click Edit and make your desired changes.

Q3: When a record is submitted to a process, can a value on the record be changed automatically?

Yes. The On Submit field can contain SQL text that is executed when a record is submitted to a Process. The text in this field is used in the "SET" clause of an UPDATE statement.