Me too, I work on a win-based PC.
http://www.prepressure.com/
a very good site to read on various stuff concerning print. I know the guys: it's really info straight out of practical experience, no books being retold.
First of all you have to aqcuire a good basic knowledge on RGB (monitor), CMYK and spotcolors (print). You think you have that?
Imo, it's best to start in black and white, in which both colours can be any colour you prefer (ie: black ink on white papaer, and red ink on blue paper). Simple things. Once you have a fairly good insight in how these are printed, you can start with colourwork, which hhas two main departments: CMYK, or full colour prints like photographs in magazines, and spotcolors, mostly Pantone, to print special colours that can't be mixed with CMYK.
With QuarkXPress you're fairly safe because many printers have it, but the pdf format is used more and more because it's more reliable and less complicated that Postscript.
Then there's the calibration of your scanner and your monitor, and getting acceptable results out of your home printer.
Which scanner do you have, and which printer?
Be shure that you can get all the help you need, or i-adresses where you find additional info, and be prepared that sometimes people may differ in opinion. You will meet that too: many printers and pros use duifferent methods. But finally, what they want from you is something they can work with, that enters into their workflow and that gives predictable results.
The biggest mistakes (hey guys, add what you consider big mistakes, ok?) are:
1/ Thinking that you can see CMYK on your monitor. No, you can't Photoshop can simulate them, but a monitor always displays RGB, and there are CMYK colours that fall outside the RGB set.
2/ Thinking that you can print spotcolors with your desktop printer. No, you can't. And thinking that you can choose spotcolors on your monitor. The only way to choose spotcolors is to take the book (ie Pantone) and choose your colour in there. That is the correct hue. If you don't: you're in for surprises.
See: the ONLY problem is that what you design on your puter has to come out of that big press and be as good as identical.
etcetcetc