A 15" diameter maple? Is that number right? Yowsers. I wouldn't considier that tree to be movable. Rule of thumb is 10" spade per inch trunk diameter, and at the larger end this usually starts to fall apart.
You'd want one of those 8 foot truck mounted spades, and even then, it's not really big enough.
The 15 gallon crab is a piece of cake. Assuming you are in land that isn't either a rock quarry or a wannabee brick factory, the hole is a hours work. Call it a 6-8 wheelbarrow hole.