Jerrie,
Without taking it out and apart, I can't say how that thing works. I'm assuming the only problem is the lack of rotation? And the rest of the oven sounds like it's working? (Can it still heat a mug of water?)
I read on-line that Apollo's phone number is (800) 330-9707. But in that same mention, it said the number rang with no answer, which might have been a discrepancy between east and west coast time during that attempt. Paperwork says it's in West Palm Beach, FL. (It's "Apollo Worldwide.")
However, for what seems to be only $99, on E-Bay, you can buy one refurbed
http://cgi.ebay.com/Apollo-Half-Time...QQcmdZViewItem
I found
http://www.repairclinic.com/0003.asp where you can tap into "Repair Help" and maybe even get parts, or call them to see if they can guide you further. 800-269-2609 What their automated help thing says is that you'll have to take it apart. And then it says to refer to an authorized repair facility... But that site doesn't specifically say it repairs or stocks Apollo.
Another good, (maybe better,) way to go would be to contact Keystone and see if they have contact info, or maybe even an oven that has a working turntable, but something else fried.
Good luck. I'd hate to be without that gem of an appliance, myself!
Steve