I'll vote for a new striker, too. Cheap if you have to pay for it, but S&W will often send them out for free (I've been told).
And sending it back to S&W is a good second idea. They may just fix it under warranty without regard to second-ownership -- without even asking. They've seen every problem in the book, and have all the parts in the world! Even if they were to charge you, it will be less than anyone else, and it will be a good job done well.
Then you can keep it and enjoy it, or sell it with a clear conscience (I refuse to sell a gun that isn't working well to an unsuspecting customer -- full disclosure if it is having any problems I cannot fix or get fixed).
Good luck getting it up and running!