The rectangular blocks use the same color coding scheme as resistors, and the base unit is pF. Those rarely go bad though, so you probably won't need to replace them. It's the wax covered paper types that are most likely to be bad, and those have already all been replaced in your radio.

You're probably right that the red wire is the antenna. I imagine it connects to the tuner or trim capacitor. Since there is no coil antenna, it is used for all radio bands. Some radios use a loop antenna for medium wave (AM) reception and a longwire for shortwave. They almost always exit the radio just like yours - as a few inches of wire with an end exposed. You should connect a length of wire to this. I like to put a connector of some type on the end, so that it isn't just a matter of twisting conductors together. But that's just me.

Wayne