Although, I am sure Henry is right on the money about this stuff, I just wanted to add my experience. I was in a similar situation a few months ago. Moved into a house, ripped up 70's green shag and my heart sank. Dog stains all over. I was not doing the job myself and had 4 "reputable" contractors give me bids. All of them saw the stains and instantly said they would not come out. Meanwhile, for the one water stain from over watering a plant, they said that this would come out. I got the floors done and the pet stains came out! The water stain did not! I thought my stains were really bad, maybe they weren't, but they looked it.