I have a basic question about reading, creating, and writing to MS Excel spreadsheets.

If I know that the computer upon which I am installing an application has Excel installed on it, does Excel expose everything I need through its DLLs to open a spreadsheet and pull data out of it into a DataSet (not necessarily in a single method call) and to create an Excel spreadsheet, populate it, save it, etc.?

Right now, we are using Crystal Reports to create an Excel spreadsheet. Is that necessary from .NET or is there a more direct route from from DataSet to .xls file?

Can someone recommend a good API/SDK for MS Excel objects?

Does the API/SDK vary much by version of MS Excel or are the exposed methods pretty consistent?

How can I check, in code, for the presense of a needed DLL that I am not distributing? I don't think I can distribute MS Excel DLLs and I don't want to buy a license.

Thanks.