Video Editor to make Website Demonstration Video

I am launching my new e-commerce site at the end of January 2011 and for marketing purposes as well as a tool for using my site, I would like some videos demonstrating how to use the site as well as a video giving an overview of the site.

This will involve screen shots and video footage using the various tools on the website.

If you have the relevant software to do this, have some videos of past work you have done, and can turn a job like this around very quickly, then please be in touch.