Comcast is required to offer self-installs per FCC mandate, you can always pick up a card if they have them in stock or make them ship you one for free if they don't.
And self-installs are usually not that big a deal since the new card rules went into effect last year [2012], pairing is usually a simple 10 minute phone call as mentioned.
Bottom line is there's really no need to pay for a truck roll, if the self-install doesn't work you make them roll a tech for free.