Need help picking out parts

Hi guys and gals, I am looking to purchase parts to repair the iPhone 4/s. While I have watched several YouTube videos online, I am still confused on which part to buy.

I will be ordering my parts on etechparts.com. My main question is if I should buy the assembly with the small parts, or without?

Is transferring the old screen parts to the new screen that hard and time consuming?

Any advice would help. Thank you.