So, I already did my taxes for 2010, and got a refund check.
BUT my mom realized that she had a 1099 that I forgot to claim.
It was worth about $1k, and I put it into my savings account (so I didn't "roll it over" into anything).
Will I end up paying in that $1k or.. (My gross income was about $53k for 2010.)

Yes, you will likely owe, at the very least self employment tax, Schedule SE. File an amended 1040.