First of all it's nice to see you advancing into the new firmware. I was on the same boat as you are now and wasn't ready to move on. Hopefully I can help you in a way where it should be stress free. I do want to make you aware that once you go to 4.4.2 you can not go back to 4.3.
Before you begin make sure you have everything you want saved( music, photos, contacts, Etc) and save them to your sd card. *MY TIPS* It says to do a complete phone wipe, format blah blah blah. Just do a normal wipe as if you were flashing another rom. Once you wipe just go back to the main menu on twrp or cwm. Restart and restart to recovery. Make sure you do this once everything is downloaded and you are ready to go. The link provided is very easy to follow and you should have no issues. Have fun and hope this helps you out a bit. If you have any questions feel free to ask.
Go to this link and download the files you will need and follow his instructions.