Do you have 2 routers facing the 2 ISPs?
In order for the fail over to work from one ISP to another, you need to run BGP with both or static (default) route with both. As for what resources you need, if you are going to be receiving default routes through BGP from both ISPs, you don't need lots of resources. If you are going to be receiving full BGP routes from the providers, than your router needs to have enough memory that can handle close to 600k routes.
HTH