I had a hard drive go out on a 2009 13" Macbook. I also wanted to upgrade the RAM from 2 Gb to 4 Gb.
Everything went "by the book". Those online guides are really helpful. Since the new hard drive was a SSD, the result was a very fast Macbook. Nice!
It might be helpful to suggest that, after installing the new hard drive, the person be prepared to reformat it.