As an AG noob, I can appreciate your "overthinking" it lol. I think we all do/did to some extent. There is a lot of good advice here. A couple tips from another noob. There are a lot of calculators to help you determine strike water temperature to get your desired mash temperature. I use 1.25 quarts per pound of water. When you heat your strike water, you have two options, both have been directly or indirectly mentioned. One is heating your strike 5-10 degrees hotter than you need. When you pour it into the mash tun, close the lid for about ten minutes. This will warm the tun prior to grain additions and the water should have dropped to your desired temperature. If it's still a tick too warm, you can add some ice cubes until it reaches your desired temperature. The other way is to add a gallon or tow of boiling water to the tun, slosh it around after covering, and let it sit for 5-10 minutes. Empty it out before adding your strike water. Trust me, the tun will sap a bunch of heat from that water warming up. If you don't preheat the tun before strike is added, or overheat the strike water to compensate for warming the tun up, you WILL drop below your desired strike temperature on this. Trust me. First thing I learned.
I also do a double batch sparge. BeerSmith tells me how much sparge water I need, and actually splits it into two batch sparges. The software also generally uses less water on the first sparge, and more in the second, but I've done alright by splitting the total sparge water between the two. This water you want right at 168 degrees (or as close as you can get), because the grain bed is already preheated so you won't lose quite as much heat as you do for the initial mash in. Between the strike water, grain absorption, and sparge water, you should have exactly what you need in total wort when you're done collecting your intial wort from strike and subsequent water from sparge to do your boil and have the right amount at the end.
A couple other things....add the grain SLOWLY, but STEADILY. Don't dump it in in one massive amount or you'll have a ton of doughballs to deal with. But don't add it so slowly that you're losing heat either. Stir constantly as you add it in. A good mash paddle or spoon is way better than those ****ty plastic paddles in my mind. Make sure you stir it very well to bust up doughballs, especially focusing in corners and other areas where grains my congregate. Once you have it well mashed in, close the lid and leave it the F alone for the next sixty minutes. Others may say to stir the bed once or twice (or more) during mash to improve efficiency, but your first attempt isn't about maximizing efficiency, it's about understanding the process. Leave it the F alone.
Remember to vorlauf well before collecting each set of runnings. Turn the valve slowly to about half way open, collect the runnings in a pitcher, and GENTLY pour that back on top of the grain bed. You may have to do this several times before the wort runs clear. ONLY when the wort is running clear should you collect it in your boil kettle. At that time, drain each running fully, shut the valve, and do the next sparge. Repeat process until done. Remember to stir the mash well, just like you did at dough-in, for each sparge. Again, REMEMBER to vorlauf the next runnings as well.
After that, start your wort boiling and do everything just as you did with extracts as far as timing of hops additions and such. You may find you get much more of a hot break with all grain, so watch for foaming/boilovers as you approach boiling and be ready to deal with them. A spray bottle filled with starsan water is excellent for controlling the hot break foaming.
Start cleaning up your mash tun and other equipment while working your boil. It will save time and is much easier to clean before the grain starts to harden up. I can clean my tun in about 5-10 minutes and then it's done. Much easier than trying to wash dried grains off the side.
Have fun! You will definately feel like you are taking more "control" of your brewing, though that can be good and bad. Worry about **** like improving efficiency and such until you have a few brews through your system. I haven't begun to worry about that, I'm more interested in figuring out the nuances of my system at the moment. The other stuff will come with time. It is NOT that difficult. More steps? Yes. More difficult? Not really.