Hey Nicole,
It's addictive, that's for sure.
The lenses you have, while decent for terrestrial/daytime work, may not end up being so suitable for night time work.
The 18-55mm closed down to f/5 or so, should start to yield round stars at the edges of the frame.
Ideally, what you need is to invest (eventually!) in lenses that are f/2.8 (or faster) -- an f/2.8 lens lets in almost twice the amount of light as the f/3.5 lens will in the same exposure time. And, if you close your lens down to f/5 as mentioned above (to combat vignetting and distortion), the f/2.8 lens will let in almost 4 times as much light. With a fast lens, your exposures can be shorter, and you get tighter looking (non-trailing) stars at web resolution.
To put it into context:
An f/2.8 exposure that yields a nice exposure at 30 seconds, would take an f/5 lens about 100 seconds for equivalency.
Having said that, there's nothing stopping you from getting results now with what you have; learn how to use your camera first, get comfortable with it, and add to your collection as your skillset grows.
Feel free to ask questions if the above was a bit confusing or if you'd like more info.
H