How do doctors get their info on medications, such as statins or sleep medications? In other words, do doctors get info from pharma or other sources?

Research. Doctors in general ared "sold" on a medication unless there are controlled trials that show us a clear difference between a medication and a "placebo" or sugar pill. Pharmaceutical company supply us with some of the research, but they also can answer questions on research about side effect rates and other things through their medical departments.
Many sources. Pdr, medical journals, participating in clinical trials with new drugs, pharmaceutical companies, peers, word of mouth, and ultimately hands on experience with new meds.