Great score! This article describes how I restored my 12-A-58:
http://antiqueradio.org/Zenith12A58.htm
If you have it restored, you'll want to do it right. A sloppy refinish job, where the cabinet comes out with the wrong colors or whatever, would decrease the value to serious collectors. Ditto with the electronics.
You could easily turn a profit by selling it, and in that case I would suggest selling it as-is. Doing a total cosmetic and electronic restoration is labor-intensive, and by the time you paid people to do that, you would have invested hundreds of dollars -- perhaps enough to eat up any resale profit.
If you don't feel like tackling it all at once, one option would be to do the electronics and enjoy the radio for a while without worrying about the appearance. It's a fantastic sounding radio for its time.
You can get a reproduction of that knob here:
http://www.renovatedradios.com/parts.html
Enjoy!
Phil Nelson
Phil's Old Radios
http://antiqueradio.org/index.html