So if I just move to the Deore MTB (M571) crankset for now, will I need to change out anything? Will the front derailleur handle the 22t (super) granny ring? I think that's my best move to begin - $89 for the crankset. Since it's a triple, no need to change anything else - I think.

Then I could get the new cassette and chain - and I think at that time, at least the rear shifter will need to be changed to a 9/10sp (dependent on cassette), right? Since the shifters are indexed, you have to run a shifter with the same indexes as gears in the cassette.

Done this way, I could get the initial benefit of the lower gearing, plus upgrade the crank. The rest of the 'benefits' are endlessly debatable but I could do that following the crankset.