The service interval for the timing belt on the 6G is 105,000, so yeah, it is DEFINITELY overdue. I'd replace it as soon as you buy the car (first thing). Timing belt replacement is labor-intensive 'cause you've got to remove the driver's side uppper engine mount and p.steering pump. Anyhoo, I think $300-400 is going quote. But since youve got timing belt cover off, it's recommended you change the water pump, too (at 130k, it's due too). I called a Honda dealer once and those numskulls quoted me $700 for both timing belt and water pump. So you should tell the seller it's gonna be $900 to get the timing belt done, see if he'll knock the price down.

FYI, if you can do-it-yourself, the water pump is about $40 and I think timing belt is $20-30. Don't pay for labor if you don't have too!!