A power trencher, or Ditch Witch, is a fairly easy machine to use. Most are self propelled. You may check some local rental stores as well as HD, as you will probably need a trailer to transport the machine and most rental stores include it in the price.
Before you attempt to use one of these monsters, be absolutely sure to call DIG SAFE @ 1800-digsafe. You must have the utility companies come and certify that there are no buried lines, wires, gas etc. It is the law, so don't forget to get it done. There is no charge for this service. If you don't and hit something, you can be liable for huge costs and fines.
A Ditch Witch usually only digs a narrow path for laying wire or pipe. The path width would be a bit shy for a good drainage system as you will not have enough width to add the proper crushed stone base and surrounding gravel bed etc.
Assuming you are installing wire or pipe, be sure to get some warning tape to install a few inches below the ground grade to warn future excavations that utilities are buried benieth. Good Luck.