The plumber said my shower pipes don't fit the Moen shower head just purchased from Home Depot. The old one was put in sometime in the 60's. True? And,because the rest of the plumbing is oringinal 1928, he's saying it could run into the thousands, "if there is a problem." Is there a converter kit for this shower head?

The plumber said my shower pipes don't fit the Moen shower head just purchased from Home Depot. The old one was put in sometime in the 60's. True? And,because the rest of the plumbing is oringinal 1928, he's saying it could run into the thousands, "if there is a problem." Is there a converter kit for this shower head?
First off, FIRE the greedy plumber, You either have a galvanized ell or a drop eared ell in the wall. Theses should be 1/2 Is there a shower arm,(see image) coming out of the wall the shower head connects to? Can you see back into the wall and tell me what you see? A galvanized ell or a drop eared ell,(see image)? This will be a simple fix. Hang in there with me and we'll have you "rub-a- dubbing" in no time at all. Cheers, Tom