I love these radios, but they are a PITA to work on. Unless you are extremely lucky, the audio transformers are both open, which means you will have to depot the catacomb, which is really fun.. NOT. And of course the shock dampers between the catacomb and the control head will be totally toast (I've yet to find a suitable replacement). Check the speaker for operation (use a 9V battery across the terminals, see if it gives a loud click), as these tend to have permanent magnets that have long since become not-so-permanent.
Now the biggie.. if what I see is all you have, you have a big problem, as the missing door contains the antenna, which is extremely critical to the function of this radio.
Now as to your question, you can get the complete owners/service manual, beautifully reproduced from the original, from
http://www.radiolaguy.com/Manuals/Radiol...s18-28.htm
I MAY have a spare door with antenna.
Note, these radios don't tune very high. The best I've gotten from them is around 1400 KHz. And tuning is very interesting, as you have to tune the LO (right hand tuner) to find the station, then the antenna (left hand tuner) to peak the signal. It takes some back-and-forth to find a station.
Have fun.
It will be like no other radio you've ever played with, I'm pretty sure.