Great pics! I'll give you my
on your questions.
1/ For the outside until you refinish it. Simply coat it with mineral oil ((drug store) to retard rust formation. It will attract dust etc. It's easily maintained by wiping & reapplying an other thin coat of oil.
2/Bare metal inside safe for food. A lot of pits are bare metal inside*. There shouldn't be anything in the metal that should impart bad tastes or other. What I would just do just to make sure is to do a burn off (highest heat) to rid the metal of anything that may have managed to impermate the metal. Then coat the the inside with a light coat of cooking oil, heat to medium/325º for 30 to 45 min to season.
3/ Temp probe bent. Does not look normal to me. Should be 90º. If it works, leave it alone. To check it, immerse ~ 1/4 to 1/2 of the probe end into boiling water & see if the reading is close to the boiling point of water in your location.
4/The motors. Just be careful with these shaded pole motors if you disassemble. Either take pics before or mark them so they aren't assembled so as to cause the motors to run in reverse... They will last a long time & start well when cold if you LIGHTLY oil the armature & bushings. I much prefer a light synthetic engine oil IE: 5W/30.0W/20. The auger gearbox might appreciate fresh grease. Try & remove as much of the old dried up grease as you can. A N1 or 2 Lithium GP grease should work well.
5/ Polish where the auger goes. Not sure about this one. Could mean inside the auger tube
If so. As long as the auger is free to turn, you are OK. The constant movement of pellets moving thru the auger assembly keeps polished. However- If there were pellets in the auger & water got to them, they would cake up. The auger would be stuck. Another long story.
To me it appears that you are off to a good start. Have fun. * Gas & stainless