Ms. Fretina,
Welcome to the forum. I don't mean to sound harsh, but you are committing the same exact sin something on the order of 75% of most posters on the forum commit. That being you are not making your assignment clear to us at all. Personally, I think you have failed to properly identify the intended use of this assignment. Your postings so far make you appear to be confused.
Are you reviewing the other real estate appraisal and to provide an opinion of value of your own using the other appraisers conclusion as a benchmark? Because that is sure the way it sounds. Providing an opinion, about someone else's opinion, using their opinion as a benchmark to say if they are remotely in the "ballpark" too high, or too low, IS a real estate appraisal! You are providing your own opinion of value in a "less than" or "more than" format relative to that benchmark. Doing so is a real estate appraisal. And the fact you do not appear to understand this does not bode well for you or your license.
If I am correct, the reality is you cannot just write a letter that sums up what you found, not unless that "Letter" is part of professional per Standard Three review plus a professional per Standards One and Two real estate appraisal. Even then that "Letter" better comply with Standard Two reporting. Any "Oral" report had better comply with Standard Two reporting and be backed up by a fully written report in your work file because you are required to be able to reproduce your report.
Don't feel badly. I see the issue of many, many, appraisers not really understanding identification of intended use, SOW, and USPAP requirements is pervasive. It is exactly why they come to the forum not knowing how to work with such a client. The moment the assignment is not mortgage form filling work, they are lost. Based on your first and following post, I think you really believe the moment a Fannie form is not required that the assignment is not for a real estate appraisal. If that is the case, you need to turn this assignment down and go back to appraisal school over again.
Webbed.