Bar Harbor, and Acadia National Park are great starting points.
AcadiaGreat seafood and Lobster anywhere along the coast,
LL Bean in Portland is a must stop for many, myself I love Kittery Trading post for sporting/camping gear.
Moosehead lake is beautiful, and the area there is largely unspoiled, about as good as it gets east of the Mississippi.
Last trips up there for me were 20 years ago, we loved Little Moose Pond area.
RV parky can show you some
rv parky