duke,
If you said how big that garage is, I missed it. 'Just some calculations on the back of an envelope, assuming a 24X24 garage:
If the average fill over the 24x24 area is 1/2 foot then the volume of stone required is about 300 cubic feet.
The 1400 lb. capacity of your loader amounts to about 13 cubic feet of gravel.
300/13 is about 23 loads.
23 loads @ 2 MPH for 2/5 miles round trip is less than 5 hrs plus scoop/dump/maneuver time.
Your time inside the barn will be short since you don't have room to maneuver much. He's going to need a rake and shovel.
My recommendation is that 5 hours (or even 10) of hard work will not hurt your tractor. Dump the first loads in as far as you can reach with the rops up and let him shovel it into the corners while you get the next load. Once all the loader work is done, gracefully excuse yourself. You'll have done enough.
If he has the stone delivered, pay a small premium for the trucks with a conveyor system to shoot it into the barn.
John