Will I kill my SERPs if I split one page into three?

I presently have a niche website that comes up first in google for its keyword combination.

It is a lengthy page, and I'd like to divide it into several pages with a tabbed interface, to improve usability for the reader as well as (I freely admit) generate some more opportunities for advertising.

I am worried that moving a large amount of info from the home page will kill my SERPs. It will all still be there, just divided among sub pages. Is my fear justified?

 

If you do it on the client-side with JavaScript/CSS, the SEs won't be able to tell the difference

 

Yeah, just use CSS.

 

OK, I use css now, but not to do this. Do you have an example website or tutorial that uses css this way?

 

here's a tutorial I put up on my site:
http://www.justin-cook.com/wp/2006/04/03/css-tabs-with-a-bit-of-javascript/