Check your heater for continuity. If it checks out, you should have nothing to worry about. Just be careful with it. 🙂
Working on the sight glass, you may find that the bottom screw is seized, or just rotted away to the point that it just breaks off. I’ve been down that road before. It’s a very careful extraction process at that point.
I’ll help you any way I can. I’ve repaired more than 100 Jensen engines over the last 25 years or so, but if you do decide that it’s too much of a challenge for you, I’d certainly be willing to take it on. 😁