You make a postscript file by printing to file using a driver for a postscript printer. you will need to choose one and install the driver to your PC. You then print in the usual way. You don't, of course, need to have the printer actually attached to your machine.
Best thing to do is choose a commercial printer, find out what printer or imagesetter they use and use the same driver - its more reliable/predictable that way.
There are others who use the Forum (e.g. Mike K) who know more about this than me and hopefully a post or two will follow....
I'm not sure what you mean by trimming pictures to get the printer driver to work. If you are using the irregular crop tool, it may create a huge file that takes forever to create the file, but it still does.
Make sure you install a good printer driver - the Lino 330 is great, and it is on the Win98 CD. Don't set your specs any higher than you need. Printing at 2450 dpi and 150 lpi for a piece that will be photocopied is a waste of bytes.
I haven't used Ghostscript, but I hear it is decent. Still, if you are doing professional print jobs, I would invest in a decent program. There are some good ones on the Net, for as little as $25. Of course, Adobe is the Gold Standard.
I have no trouble at all with Postscript files. I print to file using the Linotronic 630 printer driver (comes with Win 98) and check them using Ghostscript. I stick the four separations on a CD and give it to the printers.
I do all our advertising copy - which is mainly for PlayStation and similar magazines - using this method. I've only ever had one problem, but that was traced to a screw-up at the printers, so they ran it again for free.