Can I lay sod in the early spring ie April? How should the soil be prepared?

Yes, you can lay sod in April. Soil preparation is very important. The area should be stripped to bare soil, raked and leveled. Once the sod is laid, it is extremely important that it be watered every day in order to help the roots to get well established. Please refer to the following publication. Sod is addressed on page 6.
https://extension.umd.edu/sites/default/files/_images/programs/hgic/Publications/HG102%20Lawn%20Esta...
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