I had mine replaced 4 years ago. Dealer wanted to replace the tach too. I told them just to replace the speedo. Cost was about 400-500 bucks as I recall. If you replace it, there is no way to reprogram the new one with your old mileage. Upside, you get a brand new bike!
I would give Powls a shot (assuming you're not on the hook if they can't fix it).
Let us know how it works out for you.