A.
You can upgrade most installations using the SQL Server 2005 setup program. All report server content and settings will be fully functional after the upgrade process.
In cases where you have customized your report server deployment (added extensions, changed virtual directory settings, or encrypted the ASP.NET account user name in the registry), you will need to migrate your Reporting Services installation. In this case, you install a new instance of SSRS 2005 and use the Reporting Services configuration tool to migrate settings.
If you deployed custom extensions for Reporting Services 2000, you may need to rebuild these extensions so that SSRS 2005 can use them. Consult SQL Server Books Online for specific instructions on what you need to do to move to SSRS 2005.
A.
Yes, all reports will continue to work as they did in SQL Server 2000 Reporting Services. If you want to take advantage of new report functionality, you will need to convert the reports to the new report definition format in the SQL Server 2005 Report Designer.
A.
Yes. SSRS 2005 provides backward compatibility for Simple Object Access Protocol (SOAP) as well as URL access–based applications. You will not have to change your applications to start using SQL Server 2005. Note, however, that the new functionality available in SSRS 2005 is not available in the backward compatibility SOAP endpoint.