The one was a second generation MBA. You said it, and so did seller, this was the lower model (also older model), which seller said was different.
I would take a chance. If pay via PayPal, or most credit cards, insured against fraud sellers. Great deal I would do if seller had ample positive feedback for $1300 for revB MBA with 1.86 CPU.
Keep looking OP, and feel free to send me links to see if you "WIN" or if I outbid u, LOL, JK. Good luck finding one cheap.
They would however repair it, if it was legitimately bought and stuff. All they need is the S/N. If Apple does decide that the lines are a real issue, you can then get it swapped, but till then the story from Apple is that "it's within spec".