Arduino Temperature Controller

My project is to make a temperature controller that consists of a sensor that controls when a TEC is powered on and powered off by reading the temperature in an enclosed system; after the TEC is powered off I want a fan to be running for a set time. I also am using an LCD to display the temperature, I am using a 2004A 20x4 LCD Module Display with Serial I2C converter to display the temperature.
The sensor I chose to use is the TMP36 sensor because its one that I saw in many online examples, I am using an Arduino Mega 2560, I am using small 5V fans an a TEC 12703.
I am really new to arduino and I've never programmed anything for it before. If anyone could guide me in the correct way I would appreciate in a lot. Or help me with understanding this.

To get a temperature reading I've read this source.

For the display I found this source

Any help will be greatly appreciated.
Thanks in Advance

I am really new to arduino and I've never programmed anything for it before

But you have programmed before?

Just start small and build things up step by stepe.g.
Write a program that just keeps saying "hello world".
Then get it to output a number.
Then add your temperature sensor and output its reading checking it changes as you would expect.
Add an LED and try turning it on/off as the temperature moves between limits.
Add your LCD and output to that.
Add your fan control.

Don't try heading straight to the final solution, you will end up with lots of code none of which you trust.

Excellent advice.

That's the way to do it even after years of experience.