Finally got the B2 piston replaced.
I went to another mechanic in Denver and he was willing to work with a DIYer. He gave me suggestions on several areas to improve performance. He is from Germany and his knowledge appears to be good and trustworthy. He was willing to talk to me like I had some knowledge of cars. He listened when I said the seal on the pressure control cable to the tranny was leaking and he replaced it. Previous mechanic replaced another seal. Took it back, and he said, yea, it is the pressure cable seal leaking.
At any rate, he was able to replace the B2 piston on the 124 without removing the tranny. He said it was difficult, but he was able to do it. Other mechanic wanted to pull tranny and do a complete rebuild.
Now, that is one less thing to worry about.