That was the first thing we tried and sticking the apk file into the app folder didn't work. Every time we did it the calendar would force close whenever it was opened. EVen after fixing the permissions it wouldn't work. The only way we could get it to work was adding it to the rom. We tried installing it with a flashable zip in cwm and dropping the apk file into the system app folder with es file explorer. I could give you the file but I think it would be a waste of time.
Below is the apk file for the touchwiz calendar.
TouchWizCalendar.apk
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