Thats not going to be a fun job. On mine there is a straight tube with a 90 degree fitting soldered to the top of the reverser block. I assume thats the one you are mentioning. Where are you located? Have you ever silversoldered before? That part you may be able top patch with some tubing slit to wrap over and tie it on with wire to solder. Otherwise to remove that pipe from the reverser you need to remove the smokebox,superheater,disassemble the cylinders to lift off both the cylinder valve housings and the reverser as tey are all soldered as one unit. To unsolder that pipe you are probally going to heat ou the other joints at the same time as they hard solder the unit together and it needs to be glowing a dull red to pull off. You can use low temp solder to put a new section on but you will probally have to salvage the top fitting and just replace the pipe as Im not sure if Cliff would have just that part. He may have the complete block assembly but one never knows as there are no spare parts just damaged locos.
Good luck..
BTW don't you live in NJ too? Or was that another Dan up in Edison or near there.