True experts on Ponferrada will likely be around shortly to give you solid information, but I have such positive recollections of Galway that I could not but answer a query from a Galwegian. First, not very many people in Spain are up at that hour-- but the station café will likely be open for coffee and perhaps a snack (breakfast, as it is known in Ireland, is not a Spanish practice). Otherwise, there may be a café open across from the station. Otherwise, you can make it to Camponarya (10km away) and cafés will be open by the time you get there.
In terms of getting a sello, or a stamp for your credential, at that hour, your usual suspects of the albergue, turismo or pilgrims' office will not be open, although a café or a police station will give you one at a pinch. The turismo by the Templar castle is almost certainly not open before 9, if not 10. By the satellite map, there appears to be a church on the station side of the nearby Plaza de los Portales and, if there is a morning Mass, the priest can usually be prevailed upon to give you a sello after (or even before) the service.
Walking at dawn and the early morning on the Camino is a delicious experience, and there cannot be a better way to start.