Looks like somebody replaced the selenium rectifier. It would normally be mounted on that bracket on top of the chassis to the right of the speaker output transformer. The diode that replaced it is just a little guy, looks like a resistor but is usually black with a band on one end only. They may have also replaced the electrolytics when they did that or perhaps you did.
The tweeter in that radio is electrostatic: a PM tweeter won't work in that circuit. It's possible to rebuild electrostatic tweeters if it doesn't work. You could just leave it out, and tack a piece of hard board on the inside across where it went, to close off the hole (for better main speaker response). I'm guessing this has a 4 x 6" oval speaker? The tweeter in mine worked OK. Yours is similar to a Zenith I restored:
http://antiqueradios.com/forums/viewtopic.php?t=120245
If you Google for "rebuild Zenith electrostatic tweeter" you'll find a whole slew of articles on the subject.
Normally you tune with AFC off, then switch to AFC and hope that it grabs and keeps the station in tune. After twenty minutes or so the set ought to be warmed up enough not to drift much.
As to shock hazard: respect, but don't fear. Knowledge and attention are your lifesavers. Don't do things that might put a shock across your heart, e.g., two hands into the guts of the radio while testing. Or standing in bare or sock feet on a concrete floor while working on a live set. One side (white wire, neutral) of the power line is connected to ground. If you take a light bulb in a socket, connect one wire from the socket to power line black ("hot"), and connect the other wire from the socket to a ground like a rod stuck in the ground, the bulb will light. Same thing happens to people who go from "hot" to ground, they "light" too. Rubber mat, rubber soled shoes, if on concrete. One guy got a shock working on a radio while barefoot on his patio! Well, I guess! Common sense should prevail.