2. Can you force Comcast to give one to for self-install or do they require sending a technician to install one for you?
3. Do they charge for one?
Based on a phone conversation with them they don't seem to make it so easy.
If it were me, I would go to the local Xfinity (Comcast) Store, but then there is one a short distance from me and I can easily get there while they are open. That way, I can add TV service and get the CableCARD on the same visit. They can also show you the channel lineup for various packages available to CableCARD-using customers and maybe figure out how to bundle services to save a bit over what Internet alone plus TV alone would cost. (Alas, no a la cart channels yet.)
Generally this is more in the domain of Sales (if you aren't already paying for TV services) than Customer Service, but you might be able to do this over the Internet and you can do it over the phone.
The condo association was a subscriber to TV service, but when Comcast dropped the analog channels a little over a year ago, I went to the Xfinity Store, got my account set up for the appropriate TV service (which was at that time covered by the Condo association) but I opted for a HD DVR because I thought that once the cable went digital it would be easier renting equipment designed to record digital cable for time-shifting purposes than encumber the analog VCRs with additional cable boxes, and when I left I had the HD DVR in hand and it was a snap to hook up and, with just one activation phone call and a 10-minute wait while code loaded, I was in business, not having missed a single show I had intended to time-shift. That was far easier than getting service upgraded and then having to wait for a technician to pay me a visit on a later date to do what I could do by myself, and I didn't even have to clean up my house to do so! :) (And when the Condo contract with Comcast for TV cable ran out, which we knew it would, Comcast just added the TV service as part of the Internet+TV bundle to my bill, just as we had arranged.)