It was off but didn't finish drain/spin. There was blue detergent water at the bottom just an inch or two. I set it back to drain spin and pulled the dial and it completed fully. Pics show make/model and front panel. What do you think?

I have an old Kenmore dryer that runs but won't heat. Model 110.64964300. After removing the front bottom panel, and the fan shroud, I was able to gain access to the five things I needed to test to see which ones went bad. The thermostat, the thermo fuse to the left, and the element, the thermo cut off and the high limit thermo cut off to the right. Man they do not design these for easy access, these screws had to be removed by feel...at an odd angle with my body twisted on the floor. First question, each of these have two conductors going to it's two terminals. I removed the conductors and tested them with my multimeter. Now my question, does it matter which conductor goes to which terminal? In other words, say I have a red conductor and a black conductor going to the thermo cutoff. Once I disconnected the conductors, is it important to put the red conductor back on the terminal it was previously connected to? or if I reversed them it's OK? Second question, there was a lot of lint, partially clogging the vent duct. I cleaned the ducts, the fan shroud, and a lof of it in the cabinet. There are still some in the back of the dryer, and some around the housing of the element. See pictures. Do I need to clean all that off? Do I need to remove the actual heating element to clean dust and lint off them?