When people land on your homepage, 90 or maybe even 95% of their attention should be on your call to action.
That means: make your logo smaller. Max 3 menu choices.
Then a compelling image, your offer, and a call to action button.
Best if that button opens up perhaps a pop up so that people see the fields they need to complete after they click.
Then test the living daylights out of that headline, the offer, the colours, the image (using Google Analytics Experiments), and of course, test also your traffic system (often Pay Per Click ads).
Get it done by: http://www.websitesthat.co.uk
For: .. depends, it might only be a few hundred pounds to change an existing website, the testing takes effort though so there's that, through to whatever a website costs if you need a new one, which is anything from a few hundred pounds to tens of thousands, depends what you need