I see there was another best buy employee answering but I will to throw my hat inthe mix.
While the Sky-fi 2's are a great unit, I would also consider the roady XT, both because of thier FM modulation Range. We have a roady XT on display that can clearly transmit signal about 25 feet away, so you would have no issues getting clear sound into the car. the roady XT can also change it's display colors to better match the dash and radio colors of the car.
Both units come with docks, so you can get a Home kit or additional car kit to put into another car or in the boat.
If he travels, you might want to consider the Wired FM modulator, the "FM Direct". not only will it increase signal clarity, it will also prevent the need of searching for a better radio station once he enters a different area.
And with the possibility of a XM/Sirius Merger, there is nothing to worry, because all equipment will be compatible if/when it happens.
But for the installation is concerned, for a wireless hookup, its a matter of installing the antenna, (which can be a pretty difficult task, depending on where you put it) mounting the Radio, and plugging it in. to install the FM direct, this can get a tad more difficult, as it requires removal of the radio.
Hope this helps!