In a 17 y/o would bleeding in the Upper GI Tract have noticeable symptoms? Besides Dark Colored Stool?

Of course! Symptoms of vomiting blood (hematemesis), abdominal pain or heartburn are more common. Then there are the symptoms of blood loss: syncope/fainting or pre syncope/near fainting, rapid heart rate. The "dark stool" of upper GI blood loss is often described as "black, tarry." Any of these symptoms require URGENT evaluation. Good wishes!