I have a soderd hose bib coming off a tee from the main out front - how do I replace it?

You first shut the water off to the house and drain the system down. After the moisture's out of the line unsolder the old hose bib and wipe the excess solder off the pipe with a rag. You may now solder on another hose bib or you can solder on a on a 1/2" female threaded adapter and a 1/2" boiler drain or a 1/2" male threaded adapter and a 1/2" hose bib with female threads. Your choice. Good luck, Tom