First of all have you searched to see if your content has been duplicated? Scrappers will take pretty much everything. Try searching for terms in the middle of your content.
If it has, post your links, and whoever duplicated you on G's webmaster forum in the form of a question - "what can you do about these evil people who have stolen your content?" Make sure you can back up your claims with copies of your site on the wayback machine (archive.org) and post those links to prove age if you can.
lorelle on wordpress has an
excellent article on c&d's and DMCA.
G will tell you to DMCA the sites involved. But in the background they will
slowly start reversing some of the damage, especially if the sites are shady or have 301 page with your content. Contact the webmasters or the host companies if there is no contact information. Wait 7 days. File DMCA forms for everyone who hasn't removed your content.
Ignore sites that link back to you, unless they outrank you for your content. Point that out in G forum. They will be privately amused. Don't do anything radical to your own site unless duplicated content was syndicated.
Only then should you change your content.
If this is not the case, ask on the webmaster forum anyway. I was surprised to get an answer within 5 hours that solved a 6 month problem.