i would bring you mash water sans the grain up to temperature 170 F in the stainless steel kettle. one quart of water per pound of grain.. add you grain... should stabalize at 155 or so. let it sit on the stove or in the oven on the lowest setting for an hour. it is really not a good idea to heat the kettle after the grains are in there with the range top, you will more likely than not scorch the grain to the bottom, unless you constantly stirr for an hour..
heat your sparge water to 170 and fill your lauter tun with enough water to cover the false bottom... then gently pour your grain in. then start your sparge. and collect as much wort as you can.
if you do just heat the mash water in the ss kettle then combine the grains in the lauter tun, try wrapping the plastic pail in something that will insulate it a bit... have some 200 degree water ready to add to the pail to keep the temp constant around 155.
have fun, and remember, if a monkey like i can have decent results with a partial mash...