As a former manager of a Cable TV engineering department, I know the answers.
1. The FCC has stipulated that as of 2009, no Cable TV provider in the U.S. and its territories may broadcast an analog channel. That is, as of 2009, all television channels shall be in digital format, only.
This doesn’t mean that you must buy a new TV. What it does mean is that your TV must be able to tune to a digital channel. If it can’t, you won’t be able to watch TV.
2. The setting in the TV menu is simply one of its inputs. It might be labeled: SVID1, CVID2, VID1, or VID 2 (or even something else). I recommend that you hook up the DVD player, turn it on, put in a DVD, hit play, and then go into your TV’s menu and change its inputs from one to another to see if you suddenly start seeing video. This simply tells the TV which of its inputs to turn to. It’s possible that your TV can’t receive input from a DVD, but I doubt it.