Good luck with that. Lived in Caribou and Downeast (Washington County) for years and never picked up the accent myself. That said, having been subjected to many various skewed versions of a Maine accent in movies and TV, keep these things in mind.

1) Maine is not French and the parts of Maine that are connected to the French speaking areas of Canada are very under populated. Northern Maine and Downeast Maine are more likely influnced by British accents rather than French.

2)Maine is not part of Mass and those people that think a Maine accent equals a Mass accent are mistaken. In fact, Mainers will be offended if they think they are being compared to "Massholes".

3)Start here Youtube Video and follow some of the links on the side. These will give you a good idea where to start.

Again, good luck.