I have an old station wagon that I just bought about a month ago. I haven't had any problems with it other then the battery needs to be charge a bit if I don't run it and just play the stereo.
now I'm about to go on a very long road trip about 600 miles through mountains and valleys and another 600 back.
I want to prevent troubles on this road trip for my car.
does anyone know what I can do to make sure nothing go's wrong, or quick cheap fixes that can keep it safe.

First, replace the battery. A good one should last for hours with only the radio on. Check to be sure everything's tight in the steering/suspension. Check to see if the tune-up was recent. If the plugs are over the max spec (listed on a label under the hood), replace plugs, wires, and fuel filter. If you haven't replaced the fuel filter do it now, and do it every 30k. Check all fluid levels and condition. If an oil change is due before you get back, I'd do it before you leave rather than on the road. If any fluids are dark, change/flush it. Check the brakes, check exterior bulbs, windshield wipers, top off the washer fluid, check the tires for PSI and for any abnormal wear, replace the tires if they have less then 3/32" on any part of them. That's probably most of the list, but I do forget things.