Hi Bill,
Yes you can change them with the engine still in. It's head off, sump off and unbolt the conrods and push out upwards so the piston and conrod come out complete. Don't understand what you mean by the ladder is stubborn, are you lifting the full engine out or trying to remove the crank? If the engine was good to start with swap the conrods and build it back up unless your giving it a refurb while it's down that far.
cheers,
Stevie.