I have a 7D. I do a lot of night work. As already said, night settings aren't specific to camera brand/model, but rather to a given situation. You do not need a more expensive camera. Take a look at my profile page, especially my Milwaukee Art Museum gallery. My older work was with a 20D, and 2 shots, "Dusk at the Calatrava" and "Dawn Over the Calatrava" were shot with a 4 mp Olympus point and shoot camera. Get to know the equipment you have. I also have a 28-135. Its not a great night lens, especially because of the f stop limit, but make sure to turn off the IS when using it on a tripod. I primarily use a Sigma 17-50 f/2.8 lens.
Tripod, tripod, tripod. I can't emphasize that enough. You can't do any serious night work without one. Set your mirror lockup on a custom menu to get to it easily. Use it. Also use a remote shutter cable. You can get one on e-bay really cheap. All of this minimizes camera shake which is critical for getting take sharp night shots.
I rarely shoot at night above 200 ISO. Shutter speed could be anywhere from 1/100 to 2 seconds depending on lighting and the effect I'm looking for. For example, if you want those long streaks of car tail lights, a 1 second shutter does some cool things. Or maybe you're shooting a lit up water fountain and want silky water, 1 or more seconds is what you need. But then you need to keep the ISO at 100 or 200 for long exposure shots.
I want as much depth of field in my night shots so I try to stop the lens down as far as the light will let me. The smaller the aperture the better, but typically it'll be f/5.6 - f/8.
Use manual focus. Auto focus doesn't have enough light with night work to be reliable unless you have bright areas with well defined dark spots to focus on.
The best advice I can offer you is to just get out there and shoot, even if its not stuff you would sell. Try different things. Take your time and think about what you are doing and why. Then you'll start to get a feel for what your outfit is capable of and you can tweak your technique from there.
