Javascript / Sticky Menu / Custom Behaviour

We have a webpage based on Bootstrap, we have a 'sticky' menu at the top of the page (stays in the same place when scrolling the page). We need custom behaviour created to achieve the following:

1) When at Top of page / Default Position
Transparent background, 17px top padding

2) Upon scroll
Smooth reduction of top padding to 0px, fade up background .png image.

Should be a very simple job. Please quote a fixed price.

Can send a zip of files for immediate start.