1. If all you have in analgoeu, I would still go with the ProHD since with IT you could attach a simple smaller desktop HDTV antennae and get full HD broadcasts. It has inputs for both, cable and off air ATSC feeds. The quality is EXCELLENT, I use a small desktop antennae on mine.

2. You don't HAVE to, but see post one.
4. Laptop VGA out to tv can be done, to composite in, or dvi, or HDMI (the latter two an "older tv" won't have. quality will suffer. But, a catcher could be in your future, it really enhances the experience, remote control, speed, not having to have the pc connected all the time.
5. you will only get DL what you have UPLOAD at the location with the slingbox, so if you only have 256up, you'll only get 256 max down.

pm me for a deal on the prohd, there is a pretty good deal going on now, with a coupon of course.