A: You really can't tell unless you see the flowers. Spicebush blooms in the spring, so you should look for the flowers in March. The male flowers will be "showier" because of the fluffy, yellow pollen on the anthers. The female flowers will appear smaller because they don't have the pollen. Instead, the females will have a swollen, green ovary in the center of the 5 petals. The flowers are very small whether male or female, so it can be difficult to tell them apart without seeing both side by side. There are images online that you should look up next year to aid in identification when your plant is blooming.
Spicebush is a host plant for the spicebush swallowtail. These butterflies don't care if the plant is male or female; the foliage seems to do the job either way. Check your plant for caterpillars that are green, plumper at one end, and have eye spots that could mimic a green snake. If you find one, you have found a swallowtail caterpillar.