It is possible to tap into the audio circuit as you have suggested. I have not done this myself and I don't know how to protect a device like an MP3 player when connecting it to older tube electronics. I believe one of our members, Mr Lang, has done this. You may want to drop him a PM.
As far as restoring the radio, here is a general outline which may be helpful:
Radio Repair Hints If you decide to work on your radio, I will help you with any questions that come up. If you want to have someone work on it for you, I know of one of our members that does that work including the audio tap.
Fred
