The rod/shaft going through the case must have a lever attached to it.
A rod from the carb is not essential as this is for passing gear only.
In order to replace the seal you must remove the valve body and remove the lever.
The manual shift lever is held in place by a 13/16" nut.
Pay attention to the position of the manual valve in the body prior to removal as it must be indexed with the shaft itself.
Take pics prior to disassembly.
There is an "O" ring on the small shaft.
Dexron will be ok but you must drain the convertor as well.
There is an access plate that can be removed to drain the convertor.