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 , 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.
The trick is finding someone at comcast that actually knows how to pair the card. Not always an easy thing here in the freedom region.
Cable Cards SIKs are store pickup only. They will not ship one.
Cable cards should be banned.. Disallowed.. They cause cable bills to sky-rocket. 90% of cable cards are robbing the cable industry blind.