The answer to both of your questions depends on the medical school that you attend. Some medical schools have easier first and second years and some are pretty tough. On the other hand, some schools have tough third-year rotations and some are pretty laid back. Your best source of information is the websites of each individual school and students who attend these schools.
Some schools have gone to Pass/Fail with rankings determined by raw scores or clinical evaluations and some still have grades (letter or Honors/Pass/Fail). There is plenty of variation. Also, remember that "hard" versus "easy" is really pretty subjective.
