But even the most reputable of dealers can have problems so it is worth making a checklist of things to do to protect yourself just in case.
1st of all, ensure you have a written agreement that details what you are selling and the terms of the deal. As a bare minimum the agreement should state that the equipment remains your property until sold; that the payment for the goods, less the agreed fee/commission, remains your property; the amount of the fee/commission agreed (and, where appropriate, the limits on the dealer's discretion in negotiating a sale). In addition, you may consider photographs of the equipment to help identification, whether the dealer should be including it in their advertisements and what limits you would accept on your own efforts to sell privately (one of the most annoying things for a dealer is to have someone come into the store to look at a guitar and then for the owner to withdraw it from sale to sell privately to the same person. They quite rightly feel more than a little agrieved).
Even the best run business can hit unexpected problems so it is always worth taking a few simple steps to protect your own interests.
Hope that helps.
Largely, but not entirely, dysfunctional.