I did a successful installation of 9.0.2; answering my own questions, for the benefit of future upgraders -
1. Yes. Only the serial number is required (as is shown in the CF Admin Page of existing installation)
2. Configurations (eg: data sources) can be exported. Go to CF Admin Page, click on Packaging & Deployment, click on CF Archives. Basically, you export the settings as archive files with extension .car. Once exported from current installation, this can be imported by selecting this car file and clicking on the deploy button.
3. Server configuration can be modified (add/remove) using the "Web Server Configuration Tool" that comes installed by default with CF 9. You can find it under program files (windows OS).
I had some issues during installation. After installing, the CF Admin page would not be rendered. Basically no cfm page would load, since the extension would not be known by IIS (or the server you use). For configuring this, use the "Web Server Config Tool" mentioned above. Launch this and enable the checkbox that asks about rendering cfm pages (forgot the exact name). Once this is done, cfm pages should load. I had to enable this, and then do a reinstallation though.
-- arun