You could try one of the solutions reviewed here -
best-free-drive-imaging-program but these types of program do take some time to learn properly.
Under the circumstances, I believe the free tool -
Acronis True Image WD Edition - available to you from WD would be the best one to go for.
I find Acronis TI very reliable and their wizards are usually pretty easy to follow.
Obviously be sure to back up all your important data before you attempt the clone and HDD swap.