Fuel leak problem
 

After solving a vehicle hesitation problem by replacing both fuel filters and replacing all of the injector overflow lines, I am now noticing that diesel is leaking from the injectors, I am wondering of there are o-rings that I can replace to stop the leak or if it is an injector issue. The first and last injector appear to be the worst. I also noticed that there are what appears to be resistance coils linking what I am assuming are the glow plugs. Can they be replaced and where can I get them? I am also wondering how hard it is to replace the glow plugs?