DCC questions for Re-entering Model Railroading

Hello,
Getting back into model railroading after a 20 year absence. Going
with DCC, probably with Digitrax Super Chief (non-radio). Going to
start with a 4x8 HO layout, but will eventually go with a much larger
layout (once I move and have the room). I've read quite a bit about
DCC, it can be confusing, and I have some basic questions (my
apologies for length of append and # of questions):
My plan is to just start with a basic layout with no reversing
sections (later on add the more complex features). My first question:
1. Am I correct in assuming that I can just connect the two DCC wires
to the track (i.e. no complicated wiring required)?
Probably going to go ahead and buy a DCC equipped locomotive. Later
I'll attempt to install decoders on a few of my old locomotives. I'd
like to get one with lights and sound:
2. What is required for sound in a locomotive? I noticed some on
Tony's Train Exchange that come with sound, and it seemed expensive
(i.e. $125 for loco with DCC decoder, but $250 with Soundtrakk low
cost). Why are they so much? If I buy one of these, is anything else
required?
3. What is difference between "Soundtraxx Low Cost" and "Soundtraxx
DSD150" (this is from Tony's Train Exchange locomotive product page)?
Eventually, I'd like to actually run my trains from a computer. I
assume more equipment is needed:
4. Is it possible today, to write code that starts, stops, and will
actually run the trains? Does my choice of equipment today affect
this (i.e. does one DCC system do this better than any other)? What
programming language would control code be in? Does this automatic
control require knowing where the trains are at all times (of course I
suspect it does)?
5. Do I need special equipment to change addresses on decoders? Is
this the same as "programming decoders" that I've read about?
I'd like to emphasis nighttime / lights on the entire layout (train,
buildings, traffic lights, street lights, etc.).
6. Can I use (and does it make sense to use) my old power pack to
control some of the lights that will either be always on or off (i.e.
street lights, don't need to be controlled with a DCC stationary
decoder)?
7. I see a lot of stationary decoders listed for sale, are they
generally used to control anything else other than track switches?
My thanks in advance for any help you can provide, DCC seems like
quite an advance for an already great hobby.
Tim Giambra