You can replace the bearings, but you'd be happier in the long term to replace the car. Be sure to recondition the track. And spend the $12 for the loader. You keep it permanently, and that's not much money for the ease of use that the loader provides.

You might as well learn right now that a boat is a hole in the water into which you throw money.

Second Jake's suggestion re: McMaster-Carr for Torlon bearings, and they also have stainless parts and other plastics for other marine applications. What a kewl place McMaster is...