Reading Office 2010 documents with C#

I have an application which reads Excel spreadsheets with C# code - uses the Microsoft.Office.Interop.Excel namespace, referencing Application, Workbooks, Wookbook and Range classes.  Workds great.  Recently my development machine has had Office 2010 installed, which of course removes earlier version.  Now my application will not build - the namespace reference is unresolved.  Question - Is there a different namespace that I should now use.  Second question - if I get the first question solved, what do i need to do to ensure that my application msi package can be installed and run by somebody that has the earlier version of Office?

I'd appreciate any help.