Realize that what the experienced voices are saying is that taking apart a frame is often a lot harder than putting one together, good for learning but a major PITA. It may have been pinned and is probably put together with brass. Some may disagree but many think that a brass brazed frame shouldn't be repaired because of the heat required. Also you might be cutting off the butted sections when you resize it.
Straight gauge 4130 tubes and inexpensive pressed lugs are easier to start practicing with.