I replaced the vial tonight. All went smooth, not really that difficult at all if anybody is on the fence about it. Care and attention to prevent marking and wrecking the tube, but wasn't that bad. To start off I grab one end in a soft jaw, and the other end with a taped up adjustable wrench and twisted to break the ends free. Then some twisting while pulling up wiggled the end out. Then I just ran some water in there, and with a scriber worked the plaster out a little at a time. Less than 5 minutes had the entire broken vial and all the plaster out. Then I took a steel rod inserted up the tube, and with a firm grip hodling it, knocked the rod on the table a couple times and the other end plug came out. They're a slip fit until the last 0.1" or so, so once you get them started they don't require a lot of force to come out. This is a newer one, the older ones might be different.
All disassembled, I cleaned the tube out under water and bristle brush, then cut a clean piece of white cardstock to fit in behind the vial. Once I was happy with the way it looked during a dry fit, and cleaned the vial with class cleaner, I carefully aligned the vial and taped it's position. Then dammed up around the edges with clay so the plaster wouldn't run out (vial smaller than tube which was surprising). I ran a couple wraps of tape around the tube at both ends so I could lightly stand it up in a vice and pour the plaster in, one end at a time. Letting it set about 30-40 minutes before flipping and doing the other end. After letting the last end set up for about 30 minutes, I fit the end caps and cover back on, and pressed them together with the mill vise, and reassembled the whole thing. I'm sure the plaster was a little wet, but there's enough room for moisture to escape around the tub/vial opening as it cures completely.
I'd watched a couple youtube videos of guys doing this before, so kinda knew what I was into before starting. Had an idea anyway. I think the passage of time makes these more difficult than mine, as mine is a relatively new one. It's also different than other I've seen where the cover tube doesn't have the little spring shims, they've switched to what feels like a ptfe sheet wrapped around the ends to provide some drag. This is typical of modern Starrett stuff where it has the looks, name and price tag of old, but the feel is different, and holding them blindfolded against old stuff you could pick the new ones out 100% of the time. I'm sure the ptfe tape was an improvement in they're assembly process, they're service process, and they're bottom line, but you can tell the difference in how this one feels, compared to an older one for sure.
I didn't set out to make a post, or document this, aside from the note about the ptfe tape. but was actually surprised when I looked back at my phone and realized I'd taken a few, so here they are.
I'm into this for about $50 and 2 hours of time plus doing a buddy a favour for which I wasn't expecting anything, but he gifted me this that was brand new, but broken. There was some tarnish on the base though. A light stoning took care of that. I have not calibrated it yet. Will give it a couple days for the plaster to fully setup, and then do that.
(lol, I'll leave this up in case anyone else needs a source)
