Is the heat, Electric? Or hydronic?(water pipes)
If it is electric, it may not all be working, as it is an old system. No way to tell without an infrared camera.
And if it is water, I would remove it because it is most likely copper, and causing either condensation issues with the ceiling., or just pin holes leaking.
It is also not very cost effective. We all know heat rises, however this style worked by having it so warm it radiates down onto you , like the sun. It gets uncomfortable when you sit at a table or desk though. The heat never reaches your feet.
Yes it is stapled to the joist, right where the sheetrock(or plaster) is attached. You will need to remove it to get everything flat.
Hope this helps, good luck.
