OK - the job progresses. The Hot water pipes were clogged with so much rust and crud that I could hardly believe that any water was getting out at all. Removing the galvanized (only the parts that were in my way) was somewhat of a challenge - it had been there a long time.
Then I ran new copper pipes through the attic (easy)
But I had to rip a big hole in the shower in order to get at the galvanized pipes. But it's all new now.