Redgary - Can you please define "way too much"?
If you can do the work yourself, that is always going to cost less than if you give it to someone who makes their living working on weapons.
Replacing a firing pin, for the most part, is a pretty easy operation and you can check it fairly easily for success.
If you feel comfortable doing it, and you don't need the weapon for immediate service, so you can test it safely, I say go for it.
if you mess it up, I can assure you, your gunsmith will be more than willing to fix it for you.