First SNG - Did I goof?

[fishyak]

Decided to play "Lightening Poker" effectively a computerized $40 buy in SNG. $34 from ten, 1st 2 places pay. 500 chips to start, 5/10 blinds increasing every 12 minutes.

I've managed to survive to the final 3, bubble time. I do some pushing, move to 2nd, but Ist place stack is more than twice mine. I've got about 1000 chips and blinds are now 100/200. I have 100 chip lead over 3rd place.

Big stack opens pre-flop for 600. I know this means he has real good but not invunerable cards. I look down at AQs in spades. I'm either all in or folding. Against 3rd place, insta-call. But against the big stack - should I fold and wait for my shot to make sure I am in the money, or do I go for it with my hand against the big stack?

I went for it. Tell me what is it about SNG's that would make me right or wrong please.