I bought the AeroVironment unit that is sold on Amazon, about the same price as the Leviton unit. After considering all the others that are available, the fact that Nissan recommends the AeroVironment unit and that unit is also installed at the dealers in the St. Louis area, were the clinchers to the decision.
The installation was relatively straightforward (or so my son the electrician tells me). If your garage/house are relatively new construction (last20-30 years) your electrical service should be up to handle a 220 volt line (certainly, if you have an electric dryer, your service already handles 220 volt).
Drop me a PM or email if you are interested in my son installing your EVSE. He can probably save you some money.