I appreciate the great review!
From the first time we spoke and you told me your model number, I was sure I could fix your fireplace and you didn't need a new one. It is unfortunate (and unacceptable) that "reputable" companies are increasingly saying that replacement is the only option. The motives of these companies are clearly obvious-they make more money on new installations. That means they are not fixing older fireplaces and are recommending replacement.
On the other hand, we are a repair based business and are happy fix your fireplace with a option for replacement as a last resort.
Your repair had classic symptoms pointing to a bad valve. The thermopile had good readings (450mv+), so it looked like a bad gas valve.
However, with my 20 years experience, I will tell you that the gas valve is a problem less than 2% of the time. The pilot stays lit so we know the thermalcouple and safety loop is good, which leaves the thermopile or the valve. The millivolts are good so you assume the thermopile is good and the valve is bad, BUT, a "good" reading thermopile can short "under load". So before considering the valve bad you must disconnect the old thermopile and connect a spare one outside the fireplace where you heat it with a torch. When the fireplace works, you then know the old thermopile is bad and the valve is good, so all you need to do is replace the $55 thermopile.
Thank you Cathy for the opportunity to help you and am glad you sought a second opinion to get your fireplace fixed!
Natural Gas Technicians Inc/ The Fireplace Doctor