different header/logo's for pages/categories

[kicker]

I don't think this can be done or be done very easily. I suppose maybe with an "if else" statement, but here is what I have been asked the possibility of doing.

Condensing three websites into one theme install. Basically the initial page would be the primary website complete with its own header logo. But the person would also like separate tabs to load another page (or category page) of content which would in essence be another web site complete with different header logo. I am assuming that about the only way this could be done is if there was a series of "if else" statements that changed the header based on the url title.

Am I correct in this assumption? I also assume that it would just be better/easier to just install three separate versions of wordpress with a theme and just link from one sites navigation bar to the others.