WordPress for Fortune 100 Company

I work for a Fortune 100 company and would like to bring WordPress in to replace our current proprietary CMS and portal. I know when I present the idea people will instantly say that we don’t have any WordPress or MySQL expertise within the organization. My questions I need advice on are:

Are there organizations or services that can support WordPress itself meaning should anything go wrong with the product we can call someone for assistance 24/7? I went to Sun’s site and it looks like they have support services for MySQL of course which is great but was wondering if you can give advice on how to handle support of the WordPress product for a large organization. I know companies like Ford, CNET and a few others use WordPress today for their sites. Any other advice you can provide would be really appreciated. Thank you