Before you get into a larger project of replacing the cutter head, try to look for better quality blades.

There are different types of high speed steel, and then there's carbide. For all my woodworking, I'm increasingly going to carbide blades or carbide-tipped blades. While I use lots of HSS on my lathe and mill for cutting metal, I'm now a fan of carbide in woodcutting, because woods have silica in their cellular structure, and HSS blades will last longer cutting unhardened steel than they will cutting many woods, I've found.

You can re-sharpen the HSS blades for a planer if you have a true stone and a steady hand. 

Here's a source of parts and knives:

http://www.globaltooling.net