DR JRand. DR Ron has comented on some of your points and let me do the same.
1. My DVD's using my "S" cable will be in HD if they have been manufactured that way.
You will not want to use an S-video cable with your DVD player. It's not the best resolution possible, and if you're going to go the HDTV route, you want to feed your TV the best signals possible. For most folks, that will be the component cables (three RCA coded red-blue-green on your DVD player and on the back of your new TV. Most old 4:3 TVs don't have the component jacks and that's why you were using s-video.
2. My cable runs through my VCR but I do not have HD cable anyway. Do these TV's have an RCA connection so that I can connect my VCR?
Yes, they do have numerous inputs. Before you buy any set, you need to ascertain what equipment you're going to hook up to the TV and which jacks each piece of your equipment will use. Make sure the TV you buy has MORE jacks than you need. You want to make sure that as technology advances, your TV will be able to handle it.
3. My 5.1 Surround is a separate device that runs from my VCR and my DVD player.
For most people who have what we call "home theater," this is the norm. You can choose to feed sound to your TV or not, but a new TV won't affect your present 5.1 surround set-up at all.
4. Can I watch HDTV from my local stations over the air, will I need an antenna?
You will be able to get HDTV over the air if your TV comes equipped with a ATSC tuner (that's the kind of tuner that picks up the digital high def signals over the air). Most new TVs comes with this built in now, but you have to be careful when you buy that it has this as some companies put out high def monitors which don't have the built in ATSC tuner.
Normal TV we have now requires an NSTC tuner, but all TVs that I know about have those. It's the ATSC (sometimes written as ASTC/QAM) that provides over-the-air high def.
Yes, you will need an antenna. If you live relatively near the towers that service your area (say 25 miles or so), indoor rabbit ears should do the job nicely. You don't need to by $100 HDTV indoor antennas that some places sell. $10 rabbit ears from Wal-Mart work just fine if you're within a reasonable distance of the towers. If not, you may need an outdoor antenna.
