I have been doctoring locks for well over 30 years now and am happy to have the work. I charge $25/hour for such work and can make or repair any lock part in a period correct manner. It sounds like you have a couple of different problems as in the frizzen needs to be re-heat treated and your need a re-heat treated or a new mainspring. If that is it, that would be less than $200. For $200, I would repair and tune the lock better than new. E-mail me at mark@markelliottva.com if you are interested in sending be the lock. I am in Virginia, but the USPS would be happy to deliver the lock in 2-3 days for about $6.
Thanks,
Mark Elliott
P.S. Tom, one of the problems with heat treating flizzens is that they must be the proper hardness at the surface. Usually, carbon burns out of the surface of steel that is heated hot enough to harden. You need to add carbon back to the frizzen surface when you harden it. I use Kasenite on Frizzens when I harden them. Then I temper them to about 350 degrees. I finds that both of these things are necessary for a good sparking frizzen. Of course, a good strong mainspring is important. If the mainspring is a little weak, then adjusting the cam on the frizzen to better time the flip can sometimes help.