Anyone willing to offer advice on where and how to start this project?
The project sounds, from a programming point of view, almost trivial. The requirements are incomplete.
As the temp increases the fan speed increases.
By how much? If the temperature is 25, should the fan PWM value be zero? Does a 1 degree temperature rise cause the PWM value to increase by 1? By 10? By 100?
What part of the project do you need help with?