Assuming there are no major curriculum changes for the 2013-2014 year, your first year will have the following:
1st term: Structural Principles of Osteopathic Medicine (gross anatomy, histology, radiology, embryology and a little bit of physiology), Primary Care Skills I, OMM I, Preventative and Community Based Medicine I
2nd term: Cellular and Molecular Basis of Medicine (micro, path, biochem, genetics, cell bio, pharm, radiology), PCS II, OMM II, PCBM II
3rd term: Basic and Clinical Neuroscience (this is your introduction/transition to the systems-based curriculum of 2nd year, so you'll do micro, path, pharm and anatomy as it relates to the nervous system), PCS III, OMM III, PCBM III
OMM has 1-2 hours of lecture each week as well as a 1.5 hour lab. The time you spend on it depends on you. Some people blow it off until the week of a written exam or practical while some are diligent about keeping up with it. We do have a quiz in lab from the previous week's material, so that helps keep most people on top of things.