How tall is the willow? How thick is the trunk? If it's been in the ground for just 2 years this is the first year it will really start to grow. This is the year to move it, before it gets any bigger.
In my opinion the best way to move a tree/shrub/bush is to first determine approximately how big the original hole it was planted in was. Perhaps you remember the bucket size it came in? Probably 3 gallon, 5 gallon, or it was balled in burlap. Then in the fall you take a nice flat long shovel and cut a circle around the tree, going as deep as the shovel allows. The key is skipping a shovel width as you cut the circle. So you jump on the shovel drive it in, pull it out, then skip the width of the shovel and repeat. _ _ _ _ _ _ < except in a circle. This way you only cut ~1/2 the roots at a time. Couple months later you do it again, except you change up the pattern so you are cutting the remaining roots. You leave the tree where it is till spring when you replant it, by once again cutting the entire circle, and then attempting to lift the tree out of the hole. Depending on the species there maybe a tap root in the center that you may have to cut with the shovel or some large branch trimmers. If upon lifting you feel resistance (big tap root, or other uncut roots you couldn't get with the initial cutting (digging) you can dig a hole beside the circle to gain better access with your shovel to cut the offending root. Once the root ball is free from the earth lift the tree up and set it on an old towel or sheet that you can wrap around the root ball to assist in moving it to the new hole.
The key is to disturb the root ball as little as possible. Sometimes the ground will be too wet, sometimes it will be too dry, really depends on your soil. You don't want the root ball to fall apart.
There is debate as to what soil to use to replant a tree. Some recent research i have seen suggests to only use your native soil when planting. The logic is that if you fill the hole with a bunch of supper rich planting soil/mulch etc. the roots don't have to grow out to find nutrients. I have personally seen this when redoing several year old landscaping, where you can just walk up to a shrub and pull it right up, cause it never grew out of the original hole. Might not be an issue on a tree with an invasive roots system
At this point it's really to late to do all that, i'd just dig it up carefully, and replant, and keep it watered. The root ball is going to be heavy. You could drag it carefully in the old towel or sheet or tarp, or you could put it on a dolley or wheel barrow or wagon to move. Have fun!
Disclaimer: I'm not an arborist, i did grow up on a Christmas tree farm and have dug up 100's of Christmas trees up to 8' tall. And all that nonsense above we did not do for the xmas trees, that is stuff i learned for how to successfully dig up wild trees to use for Bonzi.
