Doing something simpler for your first all grain batch, is my first piece of advice.
Second, if you do brew this beer, do a simple Hochkurz step infusion mash. This is a rest in the 142-146F range for 20-30 minutes. Then infuse with about 4qts of boiling water to bring the mash temp up to about 156-160F and rest for 30-45 minutes. Then sparge as normal.
I like to treat all my mash water at once. For instance, I would use 3 gallons of mash water, treat it with phosphoric acid or calcium chloride/gypsum that will get me in the proper pH range and calcium, sulfate, and chloride levels (for this I use Bru'n water). Then separate out a gallon from that for my infusion. Then heat up the beta sacc rest water, which will get me in the 1.25qt/lb range for the first rest. Then infusing the gallon of boiling water will bring my mash ration up to maybe 1.5qt/lb.
Might seem confusing at first, which is why I suggested maybe you should brew something more simple for your first all grain brew.
But either way, that's what I do for my German lagers, typically.