Flying into Canada

I expect this question has been asked many times here....but here goes.

Exactly what, if anything, do I need if I want to fly into Canada?
Does the answer change if I want to land in Canada or if I am just
flying through their airspace? I expect to be on an IFR flight plan, so
I will already have a squawk code...if that helps.

The last time I contacted FSS, I got different answers everytime I
asked. I read on a previous thread that perhaps I need a radiotelephone
operators license, but that nobody will actually check for it. is that
right?

If I want to land in Canada, do I have to first land in some designated
port of entry to be inspected in some way? Do I have to land at some
U.S. inspection point on the way back to the U.S.?

Just to be concrete, I am flying from central Wisconsin to Maine this
weekend. I will likely fly over Canadian airspace. Then, when I get
there, I am considering a trip up to the Saint John/Bay of Fundy area.
If anyone knows a good airport up there, I would appreciate a pointer.

Thanks in advance!

-Sami
N2057M, Piper Turbo Arrow III