Both myself and my partner use the same laptop. The MacBook Pro has a 120GB SSD from factory. This was too small.
Easy change over. Literally took 10 minutes to swap out given I had the correct tools.
I did a Time Machine back up before changing the SSD.
Plugged that in and started up the laptop.
Ensure you have the correct tools. (Listed on the page as required when buying the SSD).
Do a back up of your SSD.
Read the how to guide.