In my experience, installing a printer on a Mac has always been a “I can even do it with my eyes closed” kind of task. Albeit most of the printers I’ve owned have been HP which are usually pretty well supported. And I have never tried to install a scanner on a Mac. I guess experiences may vary.
To makes things more transparent, Apple published a list of printers and scanners known to work in Snow Leopard. It’s very comprehensive. And if your printer isn’t listed, Apple invites you to “contact the manufaturer” to find out if it’s compatible. If it isn’t, harassment authorised.