Electronic – arduino – Thermistor Calibration

Looks like an 10kΩ NTC. Most NTC's aren't visibly branded, but the resistance at 25 degrees is the property that they are sold by.

Although chances are very slight that it is actually a Vishay part, this page lists a some datasheets for similar devices. Checking the datasheets for a similar part might give you a good feeling for how the device responds to temperature.

This would probably work, but to be on the safe side, I'd use an optocoupler, or a similar electrical isolation device in place of using a single MOSFET. The problem is the GD capacitance of the MOSFET, which, if in a case of a high frequency gate voltage rise may result in a transient voltage rise on the microcontroller pin before this parasitic capacitor has a chance to charge up.

Using a series resistor to the gate will only make the gate capacitor charge slower, so I'd drop it completely. With a FET device, you almost never need a series resistor, since the gate is not composed of a diode which you need to protect from drawing too much current, as in a bipolar device. The size of the pullup resistor will dictate how fast the parasitic capacitance will charge, so choosing it to be as small as possible seems like a good option, but it'll increase the static power consumption of your circuit considerably.