I use MO's all the time to pay off my student loan. At almost any location, it's as simple as this: You pay them the amount you want, plus a tiny service charge (usually between $.75-$1.00), and they will print out the MO with the monetary value on it. The rest, you fill out yourself, so no worries about that.

There's no risk in using a MO to pay for goods. The only thing, it will take a little longer than if you had ordered with a credit card. Other than that, it's all gravy.