Silverlight is not something that will run on any iOS device. If you want/need office compatibility, you will need to use a third party app. There are many discussions revolving around which is best and which to use.
My personal favorite is Documents to Go Premium. It has been around since the Palm Pilot days and has, in my own experience, been the best to work on documents, spreadsheets and presentations that have to be compatible with Microsoft Office. Also, you can set up a DrobBox or Box.net or even Google Docs account for free and sync your documents between machines. I have a WinXP, Win7, OSX and my iPad all sync'd up for my My Documents folders and when I edit on one, I see the changes on all.