There is no easy answer to either question. The answer to your first question will depend on the brand and model of your stand mixer, the size of the dough batch, the type of flour and hydration level, the size and shape of the bowl, the type of beater/hook, whether an autolyse or other rest period is used, and the mixing/kneading speed(s). In my standard KA mixer it will usually take about 6-7 minutes at speed 2 (and sometimes speed 3) after the dough has come together in a rough mass after adding the water, salt, the flour/yeast, and oil, which are usually initially combined at stir or 1 speed. Sometimes it can take longer if the dough climbs the hook or I have to stop the mixer to intervene in the dough making process for some other reason.
For your second question, you might want to take a look at Reply 4 at http://www.pizzamaking.com/forum/index.php/topic,2964.0.html
. To set the stage for Reply 4, you should read the posts that precede it.