He or she will be more than happy to either ease your concerns or confirm your suspicions. It's generally a good idea to include your geographic location and a phone number where you can be reached somewhere in your posting as well. Besides reassuring your potential buyer or seller that you are a real person, it's often easier to bargain and make other arrangements on the telephone than through a protracted electronic mail exchange. Some buyers prefer dealing with folks in their local area, too, as that makes it easier for them to inspect the equipment before paying money. The Usenet marketplace groups in general, and rec.radio.swap in particular, are a great place to buy that piece of gear you've had your eye on.
Items go quickly for reasonable prices.
I've sold a radio within three hours of posting the for sale message. The usefulness of these groups depends to a large extent on the people who inhabit them, though, and a few unscrupulous users can easily sink the whole thing. Whether you are a buyer, seller, or seeker of equipment, remember that your honesty and integrity reflects on the general reputation and usefulness of this forum and amateur radio in general.