Hey, a stout, sweet. I am making an oatmeal nut stout next and was instructed to perform a step mash at 122F and 153F, and to lauter REALLY CAREFULLY so that the oatmeal does not stick my sparge. What does your grain bill look like? That may give some clues as to what steps may be needed. Have fun with that one!
If you're not doing an oatmeal stout, and you're just using pale malt and other types of barley, then you could do a standard 152-155 mash for 60 minutes or so. When you're using well-modified (barley) malts, you don't need to perform a step mash. Single infusion is fine at those cases. You may want to do a mash-out at the end of your mash, though. You can do this by infusing an amount of boiling water at the end of your mash, or you could collect an amount of runnings, then boil them, and add them back into the mash for about 15 minutes. Your target mashout temp is 170.
Do not do a step mash with 2-row malt, it is not necessary especially for a stout.
It depends on the style of stout you are doing to determine your mash temp. If you are doing a dry stout then a mash temp of 145 - 148 would be good. For a stout with more body you want to be in the 152 - 155 range.