All good man. So you can use arduino’s inbuilt PWM or get a 12 bit PWM driver if you want more levels of brightness . You can pick up thermosisters for about $4, or a ready to go temp/humidity module for about $10.
This is a markup schematic of the mosfet module I referred to earlier.
These guys have a pretty good how to for using a thermosistor, code is included.