Extreme CSS challenge

We have got a set of approx 40 HTML files which we downloaded from a system that we need to restyle. The way they are written is quite clunky. The HTML cannot be touched at all, they sit inside a fixed system. There are about 5 CSS files and a handful of images (6 icons, the logo) which we are allowed to amend.
What we need from you are brilliant CSS abilities, so that you can turn the files into our design. The files need to work in Firefox, IE 7, 8, 9, Chrome, Safari.
We will supply you with all HTML files, CSS, images in the structure they will be on the site, so that you can test it in an as near realistic way as possible. We have no access to the client's system at all, so once we believe we are finished, we send them the entire files for upload and they will show us their test system and get back to us with any outstanding mistakes, so there will be a bit of toing and froing. Hopefully not a lot, as your CSS should be perfect. ; )
The last time we did this in house, we spent 20 hours on this.
Our graphic designer is currently preparing the designs. Most of the work will be subtle changes of the general look; like fonts, background colours, line spacing, button colours etc. We can show you the 2 projects we have done before.
We need you to sign a confidentiality agreement with us before doing the work.
Timeline: we can show you the files upon receiving your signed confidentiality agreement, then provide you with the signed-off design files on Friday the 16th of Dec (evening). We expect you to start the work on 19/12/2011 and deliver it back to us on 21/12/2011, as the 22nd is our last day. So you have only 3 days to fit the coding into! Even better would be if you were able to come into the office (Hoxton) but that is not necessary, we can chat over Skype.
Client feedback should be received on the 22nd and passed onto you, and we expect you to turn the feedback around asap, so that I can send the change requests back the same day. I know it is tight...
We will then be back on the 3rd of January, and the absolute final delivery day for the 100% perfect item is the 6th of Jan.