Surprises instead of surprizes is not a grammar thing, it's a spelling thing. That is how the word is correctly spelt here in the uk. Our reference book for the correct spelling of a word is the Oxford English Dictionary. Most people have a small version somewhere in their home as the full edition, updated annually, runs to dozens of A4 sized volumes. I find grammar difficult myself. Writing often seems to use colloquial expressions which break every rule in the book.