I don't know if you've looked here Steam Crazy, (or if this will help), but here's a link to the Lionel parts breakdown. There appears to be a bottom plate (#26) that is below the frame (#24), so you can access the two screws that hold the motor in place. Unfortunately, there's no illustration as to how the parts connect, or where the screws are located. But this parts breakdown might help you get a better idea.
https://www.lionelsupport.com/...mp;resultsPerPage=75
You might not want to scrap the motor. At some point, Lionel made changes to the frame to accommodate a new motor. The series one frame and motor is now obsolete and the new series 2 motor will not mount to the older series 1 frame. See this thread...
https://ogrforum.com/...5#129252226555777525
Depending on which version you have, you could sell the motor, or hang on to it if you were to ever get another Dockside switcher.
There has been parts availability issues on high end products for quite some time. But now it seems the traditional line products are NOT immune from this. The only advantage we traditional operators have, is that the products are made in MUCH larger production runs, so that buying a second product is somewhat easier. And unfortunately this may be the only avenue to acquire certain parts. Anyways, just food for thought.