a tv tuner on computer will work in any resolution as long as it fits on your screen
it is exactly the same as playing a video file, you can adjust the size of it by changing screen size, or make it full screen
you can have 16:9 ratio on a 4:3 monitor, just have black bar on top/bottom of the screen
antenna wise, it depends on your area and what kind of receptions you have
it will work on both internal and external, theorically it will even work on a pair of rabbit ears (old fashion)
but being digital, it is either you have it or you don't
so if you have absolutely crap reception at the moment, by crap i mean like black and white, ultra fuzzy etc, you are not going to have much luck!
but if you have a descend connection with just shadows here and there, some snow, it will be fine and you will get a perfect image
i would say that all the Digital Tuners on the market right now will be both SD and HD
yes it will work on your LCD i use it on my 15" and it is fine, but i only use old fashion TV, haven't got digital tuner yet, i don't think there's a good enough reason for me to upgrade yet