The danger from high voltage is that it might go through your heart, and if it does that at just the critical part of your EKG cycle, it could put you into fibrillation. Sounds scary, huh?
So the old tube TV and guitar amp guys' rule is, if it's hot or you don't KNOW it's safe, keep one hand in your pocket. You may get your right hand zapped if you touch something you shouldn't, but the worst that can happen is a burn on your skin. The zap can't go through your heart. The other danger is you develop a strong instinct to throw things if you get shocked or burnt, and this has resulted in chassis getting launched onto the concrete garage floor when a hand brushes against a hot tube. ;-(
In particular, the dangerous part of a CRT is under the "suction cup", safely insulated. You won't be near that removing the mainboard for recapping. Also, Se30s discharge the high voltage, though I'd still keep one hand in my pocket when disconnecting the suction cup if I were changing the tube or some such.