Moving from Access to SQL Server Express 2005

I have a VB.NET 2003 application which uses an Access database. I would like to upgrade it to use an SQL Server 2005 Express database because I've read that SQL Server Express will basically replace Access and make it obsolete. Firstly, is this true? Also, if I do this, will the client then need SQL Server Express 2005 installed on his computer to run my app? Will he have to have any knowledge of SQL Server to run my app? Will he have to attach the database file to SQL Server? Is there a way to automatically instal SQL Server Express 2005 (if he requires it) during installation of my application? Is it worth while to move from Access to SQL Server Express 2005?

The application is desktop based, but reads the database from the server across a LAN. Typical usage scenario is between 1 and 5 people.

Thanks