Ok, I've been through this with my cousin recently. You can go to Service Canada and you'll get a replacement S.I.N. card within 2 weeks, you can replace your Birth Certificate online, it's 35 dollars, Health Card was issued on the spot after he had his Birth Certificate, and two other pieces of idea, I think one with an address on it....all in all it was fairly painless....but then most of it was done in Barrie where it's not too busy.
Good luck
Maureen