farmallmaniac, well come to Tractor Forum!

Great to have another new member and Deere fan!
Your 4100 requires the following items to install the block heater:
part # AM101390 Adaptor Parts Eng Coolant Heater $47.18
part # AR87167 HEATER,ENG COOLANT, ASSY FIELD) $52.53
The installation will require you to clean the powder coat off the engine block were the flange bolts on so as to leave a nice clean and smooth gasket surface. Drain the radiator and then remove the drain plug in the block adjacent to the block heater mounts. Take a punch and carefully tap the freeze plug out of its water jacket hole. Be sure to grab it with a pair of pliers turn it sideways and pull it out and be carefull not to drop down inside the block. Carefully thread the block heater into the flange in a jaw shielded vice and then bolt the flange to engine block. To my knowledge the thermostat is self bleeding so the system shouldn't require purging air from the system when you re-fill it.
Here is the parts diagram to give you an idea of how they go together and what they look like. Good luck and have fun on the install!