I would like to maintain a spreadsheet of email addresses. I would then like to run a report to the workflow, use a text condition to grab a sales reps id # and use the associated email address from the spreadsheet to send an email.

My question is, what is the best/easiest method to reference the variable (sales rep #) that I have pulled from the text stream (report) and use that variable to grab the email address from a stored spreadsheet and insert it into the field in the Planet Press Image Output

You should use a Metadata Fields Management task to store your sales rep ID and create a metadata field for the email address that you want to retrieve.

Then make use of the Lookup in Microsoft Excel Documents connector in which you can specify the lookup field - i.e. Your metadata sales rep field - and your return field, that being the email address in the spreadsheet. You can then store this in the variable we created earlier which can then be used subsequently in the process in both the workflow and your image output.