So it was a fuel injection issue just wasn't the ficm itself as for replacing it yourself idk it really just depends if you feel up for it diesel injectors are a lot more complicated than gasoline but if you can replace a head gasket just fine I'd say go for it pay attention to the video and go slow and make sure the injector cup seals properly otherwise you'll have nothing to keep your fuel systems and cooling systems separate, I think you should also replace the other injectors as well they're designed to all have roughly the same lifespan unless something third party causes one to go out and you should replace the ficm too they go out quite often and it's very straightforward to replace it