How to Backup WP Theme in Event that Server Crashes?

I bought a theme and have added many gallery images and have done a lot of work to setup the theme to where it is now. I thought to myself. What if the server went down and I lost all of my work. I would have to recreate all of the posts and image galleries and that would take me a couple of weeks.

So…

Is there a way to properly backup a theme after I’ve customized it and added all of my images etc.?

Can I download the whole WP folder to my HD from the server would that do the trick? Someone mentioned to me that the best way would be using a good WP database backup plugin that creates a backup copy of everything.

I want to be able to easily re-upload everything to the server again in the eventuality that the server crashes.

Please advise on the best method…