Tom & Diane,
The first thing to do is to get yourself a good book- like Courtney Thompson's Lighthouses of Maine or Kochel's Lighthouses of the Atlantic coast.
These two have great directions and Courtney's has great photos also. You can also find directions scattered around the web-
www.lighthousefriends.com is a good place to start.
As for must see's- Portland Head (Museum), Cape Neddick, Pemaquid (now open to climb)(Museum), Marshall's Point (Museum), Owl's Head, Rockland Breakwater, Spring Point Ledge (Museum), Portland Breakwater, Portland Observatory,Cape Elizabeth, West Quoddy Head, the Shore Museum, the Bath Boatworks (Maine Maritime Museum),L.L Bean (Freeport), Acadia National Park (Bass Harbor) and about a million other places.
You'll probably be coming in from the south so include Whaleback and Portsmouth Harbor as your first stops.
I've stayed at two nice hotels in the Portland area- a Fairfield Inn in South Portland and the Marriott nearby (both have pools- FI outside, Marriott- inside).
We ate lunch twice in a little town called Damiriscotta- once at the restaurant at the Marina in town. Your right on the river and the food was good. The other one was at a nice little restaurant (name escapes me, but it's on the left hand side of the road going north right in the middle of town. Also very good food)
Hope this helps. I'm sure others with more specific info will chime in.
Dennis