My advice: don’t replace it. But be sure you understand that there’s a calculated risk involved.
Back in the days when typical timing belt intervals were 60,000 miles, I saw some belts that broke at 61K and some that went past 100K. The problem is, there’s no way to predict when your particular belt will break. As Telemark said, it may last to 150K (or longer) or it may break next week (or tomorrow). There’s no way to know.
What is extremely rare is for a belt to break before its recommended replacement interval. The suggested interval is essentially a reliable minimum mileage you can expect (barring freakishly bad luck or something actively shortening the belt’s life). Your talking about selling the car within 10 days (selling before you move, right?). The odds of the belt breaking within that period, while not zero, are very very low - problably less than a 0.1% chance. It’s rather like the lottery - terribly small chance, very large consequence.
In Russian Roulette there’s only a 15% chance of getting the bullet, but if you’re in that unlucky 15%, you’re 100% dead. Likewise, if you’re in the unlucky 0.1%, you’ll have 100% of a problem (big repair bill). This is the calculated risk. If you take it, you must be prepared to face that bill. But given the statistically tiny risk factor, it’s not a bad choice. Just be aware it’s not a sure bet.
It’s generally not feasible to inspect a timing belt. Just to get a look at it requires removing a dust cover, and then what can be seen - the outside surface of the belt, a few teeth - usually doesn’t tell much. If you really want to meaingfully inspect a timing belt, you need to take it off so you can bend it backwards and see if the teeth are starting to separate from the body of the belt. The labor charge for taking it off is probably about 80% of the cost of replacing the belt. It doesn’t make sense to pay that much just to inspect it - if you take it off, replace it.
If it were my car, I would not replace the belt.