Do it all at one time in Feb-March as you were told. I grow nut and fruit trees, chestnuts from seed, and that is when you do bare-root trees. Dig up as large of a root ball as you can, then dig the hole where you plan on planting it just a bit deeper than the root ball. There should be a basin of sorts about 3 feet in diameter (you can make a berm to achieve this) around the trunk. Then fill the basin with mulch.
If the soil won't allow you to get a root ball then just make sure that the roots are not packed together and none of the roots are turned upwards (J-rooting). Pack the soil tightly to remove any air pockets.
The mulch and water basin are critical for the first year. Don't over-water though or the tree will not develop enough deep roots, especially critical in dry climates like Texas.