I'm in the process of doing that to mine.. I have the actuator and motor if you need one..
To go to manual you have to take the actuator off and weld a piece of flat stock or equivilant to the part where the actuator goes and then connect that to the factory manual linkage.. What I'm going to do is drill a whole in my one inch flat stock and connect the linkage by using heims.
The downfall is, is that the NV273 doesn't have a neutral position.. You can put it in neutral by just going in between 2 and 4H or 4H and 4L but don't have an actually neutral like the 271s.
On edit... If you want your lights to work your going to have to cut your actuator in half and weld your flat stock to the gear, so that when you shift the sensor will pick it up. Either way you look at it, it's going to be "rigged"