Soak the rusted parts in plain white vinager for a few hours, remove and wipe them down with a degreaser. Immediately coat them in wax or other oil. Sharpen the plane iron by flattening the back, and shaping and honing the bevel. Flatten the cap iron where it meets the blade. Flattening the sole is a good idea, but not terribly essential to get started. Easiest way is 220 sandpaper, spray adhesive and a flat surface, either a piece of glass, or your table saw top.
After this, get after it. Should take you a couple hours to finish, and you'll be making shavings.
And, believe it or not, once you get it running, there is very little difference between it, and the super expensive planes made today. They'll produce nearly the same quality of work. Despite the hype.