Dear Forum,
You have been tremendously helpful with all my newbie questions. I took your advice and repotted my phal in full bloom. Hopefully I did more good than harm!

The moss it was in was VERY old! See the first two pictures of the old medium and the unpotted plant from last week. So, I ordered a new dual oxygen pot and some fresh phal medium mix of moss, perlite, charcoal and bark, watched some repotting videos and went ahead with it. I rinsed the new medium, unpotted the plant and removed all the old moss. The third picture is showing the roots - quite a few good ones, quite a few rotten ones. Then I started clipping away the bad ones. This was the hardest part for me, making the judgment call which ones should stay and which ones should go. I took off a couple of roots that were rotten in the middle but had healthy ends. Did I do the right thing? The fourth picture shows what the roots looked like after I was done. The orange color is cinnamon - I sprinkled the roots generously. Some of the roots looked dark, but were firm and plump, so I kept those. They are the ones that were on the outside before and they look grey when not wet. So, into the new pot it went. I tried not to pack the new medium too tightly. I used surprisingly little medium at the end of the day, hope that was the right decision. The fifth picture is showing the orchid in its new home. The last picture is not the best quality, but you can see that the phal is in full bloom (and a glimpse of my view of Manhattan).
So - how did I do? Please give me your honest input because I'm trying to learn from this experience as much as possible.