Answer:
No you do not. The Pastor at my church was actually a Baptist Minister before he came to our church and he did not study at a Lutheran seminary.
In Australia, the answer is yea.
There are only two ways in which can become a Lutheran pastor:
1. Attend a Lutheran seminary
2. For an elder (or other established Lutheran parish member) to go through an alternative accredited programme externally via the Lutheran seminary, in order to serve in his home church.