Hog Jaw is correct. I'm quite sure the entire helm assembly is one "part number" that gets replaced. You'll need a pulley puller or steering wheel puller to get the steering wheel hub off the helm shaft. Quite often those get over torqued onto the tapered shaft and they get locked on there pretty tight. I've had one sound like a firecracker when it came loose the "pop" sound was so intense.
I've never heard of a helm being broken, but that's just my own observation of boats I encounter. Assuming you have SeaStar Pro hydraulic steering, you're probably going to be rather careful after you replace the broken one - the cost will be several HUNDRED dollars (just for the new helm). There are a number of different ones, so be absolutely sure you get the right one to replace yours. Not doing this correctly can have a very serious/deadly outcome. You may need to turn this over to a pro for the repair as steering is not something to tinker with if you aren't well versed in doing so.
Edited by Flippin-Out (05/19/16 11:11 PM)