Ask Mr. Smarty Plants

The only member of the Magnolia family that we found that is native to Indiana is Magnolia tripetala (umbrella-tree). Its description in our Native Plant Database doesn't sound like a small tree. A couple of magnolias which are smaller in expected growth are Magnolia pyramidata (pyramid magnolia), at 10 to 20 ft. talll and Magnolia virginiana (sweetbay). The second one is the best candidate for the tree in your yard; it grows 12 to 20 ft. tall, but is native to coastal plains from Eastern Massachusetts west to Tennessee, Arkansas and East Texas. So, your plant may be a hybrid intended to be shorter, and without knowing what hybrid, we will just proceed on the basis of members of the Magnoliaceae family in general. From the website United States National Arboretum Magnolia Questions and Answers, we excerpted this information on transplanting a magnolia:

"I have a magnolia that was planted in the wrong spot, and I need to move it. Can this be done?

Magnolias have a very unusual root system. Unlike most other trees and shrubs, the roots are largely unbranched and rope-like. For this reason, magnolias tend to suffer more than many other trees if they are moved after they reach a large size. Most magnolias can safely be moved if the trunk is less than four inches in diameter. If you have time, sever some of the roots one year prior to moving your tree. Cut some of the roots just inside of the the rootball that you intend to dig. The roots will branch and help carry the tree through its establishment period in its new home. When you dig the tree to move it, dig a rootball as wide as you can manage; depth is less important than width since most of the roots are in the top foot of soil. Be sure to mulch your magnolia and water it frequently to keep it moist for the first season after transplanting."

This pretty well seems to cover your question. It is saying you need to begin preparations a year in advance, and in Indiana we would recommend it be transplanted in late Spring, so it will not have to face the cold of Zone 5a to 5b (average annual minimum temperatures -20 to -10 deg F) in a delicate state of health. That would  be not quite a year if you began to prepare the roots for transplanting now and moved it next Spring, but a lot depends on how old and how large and healthy the tree is now. 

Magnolia tripetala

Magnolia pyramidata

Magnolia virginiana