Photo #1: Note the model number of the oven is SO-2000. This is the manual, analog model, $55 dollars if the "Motor Top" is purchased as a "replacement part" from: SUNPENTOWN International, Replacement Parts for Ovens
Photo #2: The popcorn popper can be the 6 quart or the 8 quart models, the bases are identical and we only use the base. The models differ only in the size and shape of the bowl. The 6 quart models are cheaper and everywhere, eBay, Amazon, and in many retail brick & mortars. I picked up mine at Target for about $25.
The round thing is the motor which turns the stir bar. It is not secured but simply held in place by the base. The two nuts and studs you see on either side of the motor attaches the base to the heat plate. These nuts are 7mm and should be removed. The contacts you see under the base atttached to the bottom of the heat plate is a thermostat. Remove both clips to the thermostat. Carefully lift the base off the heat/stir plate and reach between and remove the stir post. There is also a thin white teflon washer in there that should be removed.
It is important to disconnect the heating function of the popcorn popper. Some people do not disconnect the heating element, and they experience much shorter roasts than those who do disconnect the heating element. One of the nice things about this roaster is the extended roast times over something like an iRoast. This well separates the first and second cracks. It is your call.
Photo #4: To disable the heating element, disconnect BOTH clips on the thermostat. Carefully lift the base off of the heat/stir plate. Only the black lead off the outlet prongs is joining the base to the heat/stir plate. Carefully rotate the base until you see the posts in Photo #5. The nuts on these posts are also 7mm. Remove the 6" white lead from its post and remove from the unit. Carefully rotate the base back onto the two securing studs. Reconnect the one remaining lead to the thermostat just to keep it from flopping around.
Photo #5:
Photo #6: The removed thermostat lead.
Photo #6: The stir motor has a 1/4" square drive which conveniently fits a 1/4" drive socket. Find a 1/4" drive socket which fits inside the drive spindle hole in the base and extends above the surface of the base. I used a Craftsman 7/16" 6 point deep socket. This socket is 2" long and extends 1/2" above the base. I found a bolt, 2 nuts, 2 1" fender washers, and a lock washer. The 7/16" socket is dropped down the center hole in the popper base and rotated to engage the drive motor lug. Then the stir bar assembly is dropped into the socket. Note that the bolt head and lower nut fit into the socket which stabilizes the bolt in the socket. The stir bar may need to be adjusted to ride level and at the proper height. Both the lower fender washer and the 1" copper plumbers cap have been notched to accept the stir bar. Use cooking foil to around the washers and nut to secure the copper cap in place. This cap is not necessary, but gives a cleaner finished look.
On the right in this photo is the black plastic spindle and stir bar retainer cap which were removed earlier.