I don't know if this has been posted before, but very good video explaining how to replace tritium vials. I'm going to do my Galil sights. You need three 1.5x6MM vials. One thing I do know is the two rear sight tritium tubes come up from the bottom of the sight, the front one slides straight done just like this Yugo. Yes, Tritium is radioactive. I know that when I was a tanker our collimator for the main gun had a tube of tritium in it (although much larger). It was a gas not a liquid (Tritium H3). I know this because one of my students shot the collimator with a M2HB .50 caliber and made a peep sight out of it. So, you do this at whatever caution level you think is prudent. Picture of MRS Collimator - he center punched it. :bang
lol https://www.youtube.com/watch?v=_NePb2KyCX0

lol https://www.youtube.com/watch?v=_NePb2KyCX0