Is it possible to replace the original RSS content? Is it possible to replace the original RSS generated for the front page by custom content?

I know how to create custom RSS channels using views, but not how to replace the original RSS.
When editing the Feed display of your view you have the Feed settings box with two settings there - Path and Attach to. If you set Path to 'rss.xml' or if you're using a view for your frontpage and you choose it in "Attach to", that should do the trick.