I was sort of off about the specs it is actually a MBP with:
2.6GHz quad-core Intel Core i7 (Turbo Boost up to 3.6GHz)
8gb RAM
750gb with 128GB solid-state drive
It's not a core i7 if it's a 2009 model...just FYI.
Modifications only change the value slightly...given the processor specs, it would probably be a 2012 model, and because of that, you're still pretty close to retail on it (especially for the top end 13" model. I can buy that model right now in Atlanta from $1,100-$1,300, but honestly, if i were to spend that kind of money on a laptop, I'd give up the extra cash and get the new model with the SSD and retina display.
Anything under $1,000 i would heavily question on that particular model (especially since it's probably still under Apple Care 1 year standard warranty...I'd be cautious under $1,100 as well.