Contaminated?

Lash night, whilst cooling my fist batch of wort, (5 gallons) something awful happened. I do not have a wort chiller, but there was snow outside. So we put it outside to cool. I later came to check the temperature, (140-150 F), and the snow I had put on top of the lid was of course melted. Because of the vacuum effect, when I lifted the lid it was a little less than graceful, I spilled to water into the wort. Along with a couple leaves... I immediately fished out the leaves with a sanitized spoon, and continued with the process.
Is my beer contaminated? Should I just toss it and make a new wort?

I would say let it go through and dont toss it until you know for sure that you have a contamination. It's not worth tossing the entire batch for a "potential" contamination. With out knowing absolutely, there's no harm in letting the yeast do their thing.

Okay I will. How do I know whether I have a contaminated batch or not?

Bad smells, weird looking hairs on it, if it looks kind of icky on top and it isnt the krausen. Look around the forum for pictures of true contamination. There's a thread floating around somewhere about what "true" unintentional contamination looks like.

Excellent. Thank you for your help. Also, I wasn't aware that I shouldn't be using an aluminum pot until AFTER I brewed. Is it going to ruin it?

It shouldnt, stainless steel is preferred though. Check out these infection pictures, some are intentional, most are not.

https://www.homebrewtalk.com/f39/post-your-infection-71400/

It is fairly difficult to contaminate your batch of beer. Beer has been mad for thousands of years without any kind of sanitation. The cold weather outside makes it unlikely that a large colony of infectious organisms made it into your beer. Also if any infectious organism did make it in then the ultra high yeast population you pitched (relative to the amount of infectious organisms in your beer) will most likely beat out those organsims

Well I appreciate your help guys. I'll definitely let you know how it turns out. But it's only been fermenting for a couple of days now.

Bigjuicy's right, if it were summer and warm, I'd be really worried. Being it's winter and cold enough for snow on the ground, it's pretty hard for bacteria or wild yeast to be present in the snow melt to cause a problem. Just watch it ferment and give it plenty of time, 3 weeks or so before you mess with it.