Template Driven Web

My client has 35 domains (web addresses) that they want to host on a Windows 2K box with IIS 5. They want one application built using ASP and SQL server, hosted somehow on the IIS so that it appears as the same application for each domain. The end user of each domain will actually be using the same application.The head of each of the 35 domain, or the jr. web master of each domain should be able to cutomize the look of the each of their domain. This customization feature would be built into the ASP application. Things that can be changed would be some text, color of text, size and color of input boxes.
This application will be similar to some of the eCommerce sites that have a web interface for their merchants to be able to modify their individual sites. Sort of selecting and modifying templates. They want 1 application so any changes and update of the application will reflect on all domains.My question is how do I start designing this?
Where can I get info on this project, any opensource stuff I can look at?
Do I incorporate XML anywhere?The domains will be accessing the same DB, how do I minimize DB trips?