can i take the entire convertible frame off, in the closed position?

You can probably directly wire the motor so it can function without the rest of the car's circuit, then you can open/close the top as you please, unless of course the motor is shot. If it's in a junkyard, have at it, take plenty of "before" and "during" digital pics if you disassemble anything, so you know how to put it back together, and tag any parts you take off so you know what they go to later on.