If you have the stem out like that, your end cap must be off to have gotten it out. Yes it needs to swivel as it is a metal to metal seal, no rubber. The tangs need to be bent just right to keep the shaft aligned. Easier to assemble the new seal, then resolder the cap back on. Just got mine from NAPA, easy fix.
I was also able to solder a new capillary tube onto my Ranco and refill with ether. NOT an easy fix.
