I've heard stories about software implementations that go on for years, costing millions of dollars. Is that a risk for my business?

While there will always be some risks in implementing new software, they are much smaller projects than the Fortune 500 companies that install multi-million dollar systems while coordinating 100's if not 1,000's of users.  Projects for small to medium size business do not involve the complexity of the large company projects so the risk is much smaller.