Create Chrome Extension - replace font on page with specific

I would like a plugin for chrome built that will let me turn it on and off as needed and it will load a very specific font to replace the once on the current page. I have a font in mind for this with - actually 4. the user controls will be on and off and which font of the 4 they want to use to replace the page with. I need to know from you if we are going to install the 4 fonts and manipulate it locally or try to inject some js in the page to overwrite text that way - whereby we can reference the font remotely. Once we are done Ill provide any graphics and design needed and you can help us get it submitted