You can open simple html in a TextField (not every html tag is suported), plus it might be a bit tricky with css.
If you get it sortet out, AS3 supports printing straight from flash. You'll find more of that here:http://livedocs.adobe.com/flash/9.0/ActionScriptLangRefV3/flash/printing/PrintJob.html
But I would think the easiest thing would be to call javascript from flash (using ExternalInterface), and have the javascript request the user to print it. GMail does somehting similar, thought without the flash.