I think you can get it within 45 days of buying your SP3. If you have a Microsoft Store near you, just go in there, show your receipt, and they'll sell it to you. If not, try calling the Microsoft support line.Is there a way to get it after you buy the SP3? I'm asking because I pre ordered an i7 SP3 and there were no options to add complete care during pre-order.
What does Microsoft Complete offer? My american express card gives me an extra year of warranty after the Microsoft one expires and 90 days accidental damage protection. I've used the extended warranty on a TV, amex just refunded me the whole purchase without asking for the broken tv back, and have used the 90 day accidental damage protection on a broken iPhone screen.