Hi Kevin,
I'm running OS 9.2.2 using a print server over our small ethernet network.
Paolo, since I'm not running OS X yet, I can't help you with accessing a plotter, but I can tell you that either you need to install a plotter driver if you're using a plotter that doesn't support Mac, (a driver costs about 5 or 6 hundred) or spring for one of the higher end plotters that do support mac, but then you depend on their potentially crude driver.
Good luck and let me know what you do.
--Tony