Okay - Here is where you could have found the information:
Face of Boe - Wikipedia, the free encyclopedia
However, I will quote them for Ya' . . .
Bonus Question - AGE: "The Doctor also makes a comment that the Face of Boe is possibly over 5
billion years old."
First time referred to being the "Face of Boe": In the episode "Last of the Time Lords", the immortal time traveller Captain Jack Harkness expresses concern about how he might look if he lives "for a million years", because although he cannot die, he is still aging, albeit slowly. He tells the Doctor and Martha Jones that it's a matter of vanity,
because as the first person from the Boeshane Peninsula to join the Time Agency, he was featured on posters, becoming known as "the Face of Boe". The implication of this astonishes Martha and the skeptical Doctor.