first, you should polish the toe of Lyman frizzen using wet/dry sandpaper. I would go to about a 400 grit finish. take a look at the frizzen currently in the rifle and you'll be able to see where the wear is: that's the part you want to smooth out on the new one. go slow, and don't use power tools. (they'll get you onto trouble much faster than they can get you out of trouble)
with the lock out of the stock, work the frizzen and watch the spring to see which position puts the spring under the most tension. clamp your spring vise on the spring with the frizzen in that position, and when you move the frizzen, the spring will be held tight and should easily come free from the lock. with the proper size screwdriver, remove the old T/C frizzen and replace it with the new Lyman, then put the new frizzen at the position of the old one, put the spring back into place, and release the tension.
shouldn't take but a few minutes. good luck with your project!