CP4 has always been an issue ( a bit overblown sometimes)... the Duramax LML guys migrate to a Cp3 using a conversion kit a lot to avoid the failure and bombing the entire fuel system.
The EcoDiesel performance market is just to small for manufactures to create "kits"etc.. plus what @Tremper126 said, the latest EPA "stuff" really puts a hurt on performance and diesels in general.
Welcome to the forum.. the good news, you'll have a very nice truck with a warranty. You can't really beat that..
I'm still hesitant to recommend a EcoDiesel out of warranty or really well over 100K, just a ticking time bomb unfortunately.
It's likely the truck will not regen with that code.. I'd recommend getting it taken care of asap. As far as replacing it, if you can identify the proper one I feel like a person can do it to save some money for sure. But emissions sensors/codes are touchy sometimes.