Definately post the price! People are skeptical from the onset. You MUST build trust rapidly. Can't do that if you are hiding your price. Makes people wonder what else you are hiding.

Beyond price, state things like ordering times, calculate shipping costs for them, any taxes etc...
Be upfront and believe in what you are doing at all levels. The more you make clear before the sale the fewer problems crop up after you accept their money. Just make absolutely sure you deliver on your promises.
If you state allow 3 weeks for delivery. You'd better get it shipped so they will get it in 3 weeks or less. People need to plan things based on your word. I am assuming you may need to purchase the items on an as needed basis. So you will need to charge the customer well in advance of shipping the product. Make it clear when they will get charged so they aren't expecting to be charged just prior to shipping. This single misunderstanding can spoil an order.