Hi Fiona and welcome to GoY. A 7 foot high tree is not going to take kindly to being moved, the root spread will be as wide as the canopy. If you have to move wait until it is dormant prepare a huge planting hole then, and only then, lift and replant, you'll need to watch and keep watered and are still likely to lose - sorry. Soil needs to be the same as what it is in right now.

Commercially machinery would be used to cut an enormous root ball and sever the tap root then transport it to theprepared site.

Youhaven't said which varietyof acer or how long its been planted.

If you have lots of time it is sometimes possible to move big trees but it takes three years. First year you dig down one side and sever most roots. Second year do the same on the other side . The tree shpuld respond by putting out a mass of smaller finer roots. The third year you cut the tap root and move the tree. But it will probably be unstable with half its big roots gone so precautions need to be taken. Don't suppose this is any use to you but its interesting isn't it? I used to wonder how parks depts etc were able to plant big trees successfully.!