Now you know why plumbers are paid so much!
I would not attempt to weld the pipe, especially the galvanized. Sweating Copper pipe is easy and like Rambo said cleaning is the key to it because any oxidation left on the joint surface will most likely result in a leak, this however is no big deal and is only a matter of paying attention since cleaning it is easy. You can probably get the brushes where you get the pipe or at most any hardware store.