Let me tell you one thing. From what you posted, it seems the company who designed your website don't know how to design a website using css and/or template system. If he had used a template system, he could have completely kept the design and application different. So changing the design at one place would have gave the website a cmplete diferent look. Even he would have used css prpoerly, changing the css file should have solve the problem.

Not only that, he could have created the css files dynamically, depending upon the browser size of the visitor. Charging $1500 for that small change (big for that company, because of improper planning of site) is too much. It is a job, that can be done in 1 hour if it would have been coded properly.