... I'm really having trouble focusing the camera on night mainly because I can't see anything on the LCD. ...
To achieve good focus, star trails photographers will usually use the "Live View" feature of their camera to prefocus on some brighter object at infinity (eg, lights of a distant city or radio tower) and then re-aim their camera in the desired direction without touching the focus. I actually bring a roll of low-stick painters' tape with me, and use a piece of it to lock the focus ring. You should set the focus only after the camera has stabilized to the outside air temperature. This is because expansion and contraction of the optical train with changes in temperature can change the focus slightly.
Also, you have to realize that that the photography of star trails is extremely demanding, and kit lenses like the one you are using are never terribly sharp wide open. For this sort of work, one wants a very low f-number lens that is sharp wide open or nearly wide open. If you only consider modern lenses, such features can be costly. However, older, used, manual focus, non-zoom, fast lenses can often be bought at very reasonable prices, so if you want to pursue this, you may want to consider getting such a lens. They also typically have much tighter and smoother manual focus, and you don't have to worry about "zoom creep", ie, the focal length changing during your exposure because the lens is pointed up at a steep angle.
Finally, don't be shy about using software to improve a soft image. For example, many years ago, I took the attached image in a dark-sky area in upstate Pennsylvania using a borrowed, legendary, old, and very costly ( > $3000) manual focus
Noct-Nikkor 58 mm f/1.2 on one of my d700 bodies on a tracker mount. I stopped the lens down to f/1.4 to maximize sharpness. To improve the resulting image, I used a combination of noise reduction software on the NEF file, followed by two passes through "Focus Magic", one pass to reduce any residual linear motion left by the tracker mount, and the other for general de-blurring. I dug into the shadows with tools like curves and shadows/highlights to fill the image with stars of all magnitudes by giving me a more logarithmic response to brightness instead of the usual gamma function response curve. The final step was to composite in some silhouetted trees at ground level because when using a tracker mount, anything on the ground is blurred -- only the stars stay stationary in that frame of reference.
HTH,
Tom M
PS - You should realize that it's a lot easier to get good bright night sky pix when the stars are stationary (because of the tracker mount), than it is to get star trails when the same number of photos are spread over a long curved line of pixels, not just a small area.
