Evaluating Medicare insurance plans can be a challenge, but trained volunteers are ready to help. Sam Likens, Douglas County program director for the Retired Senior Volunteer Program, said volunteers can help seniors find the Medicare Part D drug coverage best for them. Without a Part D plan, seniors on traditional Medicare plans do not have coverage for prescription drugs. Seniors on Medicare can sign up for or switch Part D plans beginning Monday. Open enrollment ends Dec. 7. The same enrollment period allows patients to sign up for Medicare Advantage, a form of Medicare insurance. Medicare doesn’t cover all expenses. …