Jestocost was right in the ballpark. You could take the ferry or resort monorail. The ferry stops first at Grand Floridian. The monorail stops at Contemporary and TTC. So, the time is about the same either way.
With perfect timing, it's a 10-15 minute trip. But, there are the inevitable weather delays or monorail malfunctions that can add to it.
I agree with being out MK's gate at 3:45.