Porter, sorry to hear the news about diagnosis, but now that you have more information you can at least formulate a game plan.
My wife Lisa got a second opinion at Mayo (Rochester) shortly after her first visit at OHSU. You can definitely get a second opinion after you start chemotherapy, but some centers may want you to wait until after a few cycles are completed. We were very impressed with the Mayo system, the doctors, and the overall efficiency of the 3-day visit. Unfortunately, the Mayo team simply confirmed the opinion of the OHSU team that Lisa was inoperable and unlikely to ever be a candidate for surgery.
However, since that time, the OHSU team has shifted their opinion a bit and now they believe that Lisa may be a candidate for surgery in the future. Lisa's condition is quite similar to yours -- ICC with a large 15cm mass and several smaller masses. The only difference is that Lisa is stage 4A due to local and distant lymph node metastases. Dr. Billingsly is the liver surgeon at OHSU and he is one of the top surgeons on the west coast -- he trained at Sloan Kettering. Dr. Billingsly reviewed my wife's scans at the tumor board and he believes that resection is possible with a good initial chemo response.
We have also sought multiple other opinions from surgeons who essentially agree that resection could be possible in the future. Some surgeons will review your scans and will provide a remote consultation without actually having to visit them. Please let me know if you would like further information and I can provide some names and contact numbers.
The takeaway from my rambling is that second and third opinions are incredibly valuable. Just because you have been told that surgery is unlikely does not mean that you will not become a surgical candidate in the future. And like I stated previously, many of those who have been deemed permanently inoperable have had very good outcomes and live productive lives largely free of symptons.
Best of luck on your journey, and please let me know if I can help in any way.