Where Can I Find Customizable WordPress Themes?

I would like to find either a wordpress theme website or a wordpress plugin that would allow me to edit my header by replacing the default header title with my blog title without changing the code. I do not know how to read code, let alone change it so I am looking for something simple that would allow me to edit the theme from my wordpress back office. I am finding alot of themes that I would like to use but when I upload and install them, it’s not coming up with MY blog title. I hope this makes sense. Can someone please help?? I am spending way too much time on this.
I have tried the WordPress directory but they dont have anything that I like. I would like to purchase a premium theme but I want to make sure that I will not have any problems trying to edit it or it will be a waste of money and I’ll still be in the same boat.