They will expect to take possession of the damaged item in return for the payment. Filing a claim and obtaining restitution can be a long process, so be patient. Its worthwhile to confirm everything agreed in phone conversation in writing as well. Take a photo of the damage right away so that there can be evidence of a date and time to demonstrate that it was there upon opening and you did not have time to cause the damage. Report the damage immediately.
Emails record the date and time the mesage was sent.
Ask the seller if he will agree to refund the money if there is damage since the seller is usually the one who gets the insurance money. If the seller offers an evaluation period or a guarantee he may still refuse to take back the item if he does not feel it is a bad problem or if he blames you for causing it. Try to clarify this with them. The bottom line is that Astromart has been the most successful Astronomy Classifieds on the Internet because of trust. We want to encourage everyone to help maintain that quality as more and more people take up Astronomy as a hobby.