Andy, I'm no expert by any means...but I do think you can take them apart...check out
www.toploaderheaven.com ....it talks about how to disassemble them, diagnose them, and clean them. Also, I think you can change shifter handles pretty easily....I think it's just a big pin that goes through the bottom of it that connects it...
Some of the other knowledgable members can add a little more.