Help re changing page names

I'm an amateur web master (only of my own domains) and I want to change some names of my pages to incorporate keywords.

Here's an example:

My main site is www dot generic.com
A current page is generic dot com/writing.html
My keyword is "resume writing" so I want to change the name of the page to:
www.generic dot com/resume-writing.html or resume_writing.html

If I change the name in this fashion will it hurt my google ranking or help it? I am thinking in the long run it will help it but in the short term, any links to that page will no longer work...

And is there some kind of form I need to fill out at google and/or other search engines for this name change so that anyone going to the former page will be redirected to the new page? How/where do I do that?

My main question though is Will changing the name of the page(s) to include my keyword be helpful to my google ranking or should I just leave well enough alone and maybe create a couple NEW pages that incorporate the keywords.

I am thinking it is helpful to ranking because my competitors who have higher ranking than me have incorporated the product name into their sub-directory pages and I have not. I am sure there are other factors as well but I am wondering if I should make this change and if so do I need to fill out a "redirect" form or something at google? I have heard this term but know nothing about it...