I doubt you can embed excel in your WPF, you might want to look at something like Spreadsheetgear, they advertise pretty heavily here. We were looking at them for winforms and they looked pretty good at the time.
Tracking changes on an excel sheet is not a trivial matter, there are a number of commercial apps that do this on an enterprise level and they are VERY expensive!
Link for info about
SpreadSheetGear[
^]