Your inside wire must be permanently disconnected from Verizon. Typically
the Comcast tech will cut the wire going into Verizon's gray box to
eliminate the network interface.
If your eMTA (cable modem with telephony) is in a room in your home,
it must be located reasonably close to a telephone jack. Your inside
wire is then backfed from this telephone jack. They can plug a splitter
into the jack so you can still plug an extension phone in.
Assuming you own your own router, you'll want an eMTA with DOCSIS 3.0
without a built-in wireless router like an Arris TM822G. My experience
trying to obtain the correct eMTA was pretty bad; I reported on this a
few months ago. The techs had no clue as to which ones were DOCSIS 2.0
and 3.0, so before the tech disconnects your current cable modem, look up
what the tech proposes to install on Comcast's list, because they take
a painful amount of time to register themselves on Comcast's network,
like close to a half hour.
Before the installer shows up, make sure this instruction about which
eMTA to bring makes it onto the work order: eMTA DOCSIS 3.0 without
wireless gateway (assuming you own your own router).
Is maintenance of inside phone lines covered in your area? I have
absolutely no idea. You'll have to negotiate for that if that's what
you want.
btw, long distance, both in state and out of state, is amazingly
cheap these days from long distance providers you can get with your
traditional land line. I use TCI and Pioneer Telephone, but there are
others. Comcast Triple Play includes their notoriously overpriced VoIP
telephone service. Are you sure you'd be saving money?