Theology is to ministry as mathematics is to engineering. To study math you need a math book (or a bunch), a computer (I presume), some pads and pencils and a good instructor. In enginnering you need far more: a product or concept, raw materials, mathematics, physics, electrical theory, marketing, testing and evaluation, maintenance and improvement, materials handling and storage, probably an office and staff, maybe a labratory, etc.
In theology you need a Bible, some knowledge of original languages, a theological library and a small community with whom to "do" theology. In ministry you need far more: a target focus or ministry field, a calling, spiritual gifts, theological training, a working knowledge of the Bible, hermeneutics, church history, a basic library of books and/or software, communications resources (e-mail, an adequate ability to write, a computer), a working knowledge of psychology and sociology, a team on which to work, accountability, commitment and integrity, a prayer base, stick-to-it-iveness (determination,) thick skin, a personal sense of security, mental health, significant social skills, a home base of operations (some location), some equipment, faith and a love for the people in the ministry field.