For period service documentation for that set look for a Sam's Photofact for that TV chassis number, and the radio chassis number (Sam's liked to separate the radio info for combos).
The info will not tell you how to troubleshoot/repair the set, but will tell you how it's wired and give you adjustment procedures and voltage/signal info for a properly working set that you can compare to the measurable voltages and signals in the set to find errors.
The following site is chock full of servicing info for beginners, and examples of restorations.
http://antiqueradio.org/welcome.htm
These forums also contain a lot good info if you do a lot of reading.
I recommend you fix the audio section first, if it is not working (otherwise get an AA5 tube radio to practice on), since audio circuits are simpler for a beginner to tackle.