infrared temp sensing project

Ok so my first project was over my head for now.
Can you fellas offer some guidance with another one.
I would like to sense temperature reliably with an infrared sensor and at a set temp(about 140f) trigger a led.

Is this super hard, what parts are needed and is the programming relatively simple

thank you and I look forward to completing this one.

I made one using a MilCandy and a grove sensor but it is only reliable when hooked up to a laptop, standalone consistency is poor

google "arduino ir temperature sensor" for several examples