Yes - I agree with the previous answer.
1. Go with either Nikon or Canon. Usually people have a preference to one or the other. But, these two manufacturers are the choice of pros. The best way to find out is to go to a camera shop or somewhere where you can handle both of them and see how the controls are laid out.
2. Yes! By all means don't skimp on your lens quality. Light is the most important thing in photography and the light passes through your lens elements. So, you want the best you can afford here.
Any model of Nikon or Canon camera will be a good one, but the lens you put on the camera will make a big difference in your photos - especially if you blow them up to any degree. If you buy a Nikon, put Nikon lenses on it. The same with a Canon - get Canon lenses.
If you do get a less expensive Nikon or Canon camera, it is not a bad choice. You can always move up to a better model later and your lenses will still fit your new camera. And, you can keep your old camera as a backup.
If you are going to do night time photography, then you want a camera with an off-camera shutter release so you can set up your camera on a tripod and then release the shutter. (You can also do this with the camera's timer, but you will find that the off-camera shutter release is good for other things, too.)
3. Did I mention a tripod? Get a good solid tripod and learn how to use it. You mentioned night shots, so you will need a good tripod. Don't skimp here. Get a good one. It will last for years.
Bonus: A good solid quick release ball-head for your tripod is also a good investment. Do some research on these. There are a lot out there. But, these are a very good accessory to have. They make a big difference in the field.
B&H camera and video is a good on-line store to go to to look. They have a good selection and you can compare features because the list a lot of specifications. (It's not a bad place to purchase equipment, too.) And, manufactures' websites also list a lot of specs for their equipment.
Flickr: Go to Flickr and search for photographers that do work that you are interested in doing yourself. I was trying to find the one guy I just saw there who just started shooting through a telescope at the night sky, but I could not find him again. Most people on Flickr will list what equipment they use in their profile. And, if you write them a polite email, they may answer your questions. Don't be afraid to ask other photographers for help. That is what you get in photography magazines, right? Photographers sharing their knowledge.
Photography is about two things:
1. Seeing something you want to capture on film/pixels. This is the creative "seeing" side of it. This is what causes you to raise your camera up or set up your tripod in a particular spot.
2. The second thing is having quality equipment and the knowledge of how to use it in order to capture what you see in the first place.
Happy shooting!