Cook lasagna noodles according to package directions or until tender but still firm. Drain, keep warm.
Meanwhile, saute the sausage, and onion in a large heavy skillet or saucepan until sausage is done. Add sauce, salt, and mix well. Simmer on low heat 12 to 15 minutes.
In a separate bowl, combine eggs, ricotta cheese, and oregano.
Grease a 15" x 12" or larger, deep sided baking pan.
Arrange a first layer of noodles across the pan so the ends hang over the sides. (The ends will be laid back-over the top for the final layer. This helps to hold lasagna together when cutting servings) Then add a layer of the cooked sausage lasagna sauce, ricotta cheese and mozzarella cheese.
Add a second alternating layer of pasta (lengthwise in the pan), the meat sauce and cheese mixture.
Repeat until pan is almost full then fold over the ends of the first layer of noodles and top with more lasagna sauce.
Sprinkle with parmesan cheese and bake at 350 degrees for 40 to 45 minutes, or till cheese is bubbly.