Hi Robert -- I double-checked and the windows lift right out of the track once they are unlocked -- both the sliding and the fixed side. Thanks for mentioning it though in case I had not checked!
I am still so intrigued/amused (?) by the variety of responses on how to get it down there.
Good question! The garage is ground-level, right side of the house; basement is below grade and the window is at "half" grade...no doorway between the two.

All true! And I'm an Air Force Reservist LOL.
It came this morning -- having seen it in person now, in the words of Elon Musk, it's an "absolute unit". I can definitely see how taking everything off the tank will be beneficial, and will be doing that.