Upgrading Index Questions

We are upgrading from EV for Exchange 9.0.4 on server 2003 to 10.0.4 on 2012 R2.  We had a consultant in about a year a go talking to us about the process.  We were told that all the indexes had to be converted to 64 bit at the time of the upgrade and would be offline until the conversion was complete. My research indcates that this is not the case. My questions would be.

1. In the upgrade process new 64-bit indexes are created for new content and co-exist with the 32-bit indexes and the system is avialable for use and do not have to wait for the existing indexes to convert.  Is this true?

2. When we choose to convert the 32-bit indexes to 64-bit is the system still available for use during the conversion?

3: I am going to use the Migration Wizard to assist in the upgrade.  Will I be able to choose a new volume for the 64-bit indexes or will they  go to the location of the existing 32-bit indexes?

Thanks for your help in advance.