I have just started freelancing web sites and wanted to start off small but lo and hold, my first client is asking for the biggest project I have ever faced. In short here are the parameters of the project:

1.) Client needs redesign for existing website which is 200-300 pages in size
2.) Client is at top of google search for a pretty general search phrase and wants to keep his high ranking
3.) Also wants CMS functionality on a few select pages.

I can code in html, css, and php
My questions are the folllowing:

a.) In general, for a average web designer, approx. how long would it take to convert 200-300 pages of html to a newly coded design.
b.) any ideas on professional ways to charge for this
c.) any ideas on how to accomplish this with out affecting google rankings
d.) any ideas on how to integrate CMS functionality on a few select pages without having to redesign entire website in, for example, Joomla

I would really appreciate any suggestions as I feel like I;m about to have a heart attack.