Welcome to FlyerTalk!

The 767 is a perfectly fine, safe aircraft. It most definitely is well suited for the trip - otherwise the airline wouldn't use it...and the pilots wouldn't fly it (after all, they're inside the plane too!)

It is smaller than a 777 but that's a relative thing. It's still a "large airliner", if that's a concern to you. Smaller aircraft than the 767 are used for transatlantic airline flights, in fact.

A google search will show you plenty of pictures of the 767 inside and out, maybe you'll feel better seeing for yourself.

Bottom line, relax and enjoy your trip!