Drained and refilled 93 Classic and it heats up fine. Jet pump control causes motor to hum but nothing else. It has frozen in the past and repair folks put a wrench somewhere to loosen up what apparently is a rusted motor. Any advice on what I can do to free up the motor?

If there is room you may be able to take the back cap off. Usually the shaft is slotted and you can use a 7/16th wrench to jockey it back and forth a few times. Sometimes the wrench is tough to fit in there though.

Thanks Dan. I took the cap off the pump motor and all I see are electrical parts, no slotted shaft. Am I looking in the right place - the end cap has two screws holding it on at top and bottom.

Yeah, that's the place, but there's a lot going on in there. If you turn on power and hit the jet pump button for a second you'll see the shaft/armiture spin or try to spin slightly.

Finally got the motor cover off - had to remove what looks like a capacitor to access - but there is limited space to turn the shaft - only about a quarter turn each direction. End result is no luck - still the same hum. Is this a motor that can easily be replaced - I'm moderately handy - I assume the motor is not on the 'wet end'. Any help will be greatly appreciated.

You can do the replacement yourself. I'm assuming that your pump looks something like this:
http://www.poolsinc.com/images/parts/sc427.gif

Given the age of the pump, you'll probably want to go ahead and replace the housing o-ring (#6) and diffuser o-ring (#14). You'll also need to order a new shaft seal (#8).

Down to the impeller, the disassembly is pretty straightforward. To get the impeller off you'll need to grab the shaft from behind as before and then turn the impeller. You may need a strap wrench for this. If you notice a bolt in the center of your impeller it is reverse threaded so remove it first.

From there, remove the seal plate and the old seal. Put on the new one the way the old one came out. Connect the seal plate to the new motor. Put the impeller back on and tighten it, then reassemble and wire it up.

Sometimes the impeller gets destroyed in the process, so you may want to go ahead and order a new one in advance.