I want to change H1 to H2 in a contact form

On this page, the second "Contact Us" is an H1 and I want to modify it to H2 as it cause a duplicate H1 on the page (SEO issue/warning).

https://www.hiatt-hardware.com/contact

I found the phtml files on the server. My question is: 

Is it enough to update the files and replace H1 with H2? Do I have to do anything else?

Thank you

Dan