I'm afraid this receiver has more issues than just this part, although I am grateful to now know what it is. Thanks!
I re-soldered new leads to the old cap body very carefully, and put it back into the circuit, but alas, the problem persisted. I then swapped a 68, and then a 100 picofarad (I couldn't find an 82) ceramic capacitor in place, and no change. It's something intermittent- it crackles when warming up and works about half the time. When I slam the chassis in frustration, it works, then slowly fades to silence... I've replaced every part I can think of and re-soldered every solder joint, tried different tubes, triple cleaned and tightened the sockets, replaced wires, all the electrolytics, most of the paper/foil caps, doused it in holy water... Definitely some evil black magic goin'on! I think WiseOldTech was onto something with his suggestion of this becoming a shelf queen. Too bad it's aesthetically unpleasing!
After giving it one more try and producing nothing but smoke and hurt feelings, I have officially given up... Not much on the radio anymore anyway.
Many thanks to everyone's help and all the great suggestions!