Welcome to AG brewing. It's much easier than you make it out to be in your head.. Ideally, it's the SAME process once you get the boil going, with the matter of just doing a little calculating and some measuring of water.. Temperatures are the most important when you mash, so keep that in mind.
Go slow.. you will add roughly 1.5/2 hours to your brew day.
If you've done partial mashes, you are familiar with keeping temps right for your grain and the times. If you have recipes you like, get a program like Beersmith 2, and you can put your equipment in the profile, it shows you online on the site how to do it. Program looks... confusing as hell at first, but trust me, watch the videos and play around. It's a great tool that makes your brew day easier for sure. You can use a trial version of it for a while before you buy it, and it's not expensive.
The program will also convert your recipes from extract to all grain somewhat. I'm not familiar with that, but people here use it all the time. It's pretty simple from what I've played with.
Fire away at your first recipe, or find one here.. I started with a simple IPA, if it came out low, then I had a nice pale ale...
Basically get your tun, use the beersmith that will tell you how much water to heat up, and to what temp. Add it, then add the grain, and stir like mad. Check the temp and get it where it needs to be for the recipe. Close it up and forget it for an hour. Then you drain it slowly into a pitcher until it runs clear and slowly let it fill your kettle. Add back the cloudy grainy wort in the pitcher to the tun, and empty the tun out until it's gone.. While you mashed in for an hour, you should have heated up more water, beersmith calculates what you need there too for the size of your recipe, and to what temp as well. Add the sparge water, stir like hell. I let mine sit for 10 minutes to settle back, and then repeat the process. Drain it until it's clear and let it fill the pot to the volume you need for your boil.
If you want a 5.5g recipe, and will lose .5 gallon in the kettle to trub and break material, you need 6 gallons of wort when you are done. But you also need to figure how much you boil off in an hour.. Say.. 1 gallon.. So you need to start with 7 gallons of wort, that will boil down over time.
Volumes, Times and Temps... Go slow.. you'll wonder why you fretted about it in the first place.