1 - Depending on your source material you MAY be able to see a difference at that distance - I have dist of about 8 ft with a 40" and i do see a difference betw. 720p and 1080p, but I am very picky. And this is with Blu Rays.
These days, the price difference betw. 720p and 1080p is not much, so I'd say, for future plans like Blu Ray and HD streaming, spend that small amount and go with 1080p - otherwise you might regret it later.
2. You can connect a laptop via VGA or HDMI (best quality) to the LCD TV. For tis the TV needs a VGA (pc) input, OR if your laptop has HDMI out, and HDMI input (most TVs have several of HDMI inputs anyway, and they will also have VGA input also) - so in this case you are just using your TV as an external display. Make sure your laptop has one of those video outputs (some might even have S video, but it's not HD)
OR: you can get a Blu Ray player, which can be connected to the internet easily via your router (most BR players off this function these days) and use the built in Netflix or amazon or Vudu feature (needs account, but you already have Netflix account) to stream movies in HD. a lot easier and direct and quality is also better than going through a laptop with a mess of cables, etc...
I have a Panasonic BD65 which is great for this type of thing, and it's under $100.
you can connect the 2-ch audio out of a BR player to your amp/receiver for audio.
If you use the laptop, I guess you can use the headphone out jack the same way...