Question is, will I have to mess with the injector to replace them? Repair manual says to remove the tube first before the injector. Reason is, #3 and #4 lines, they have a little corrosion where they make up to the tube. I'm hoping I don't have to replace the lines as well.

 

You shouldn't have to. I'm no expert but from replacing them on my truck I can't see why you need to. If you want to be sure I would take the valve cover off & loosen the two injectors. Then replace the tubes while tightening the tube & injector just like you would if you had the injector out. Just my opinion.

 

Per Cummins, everytime a crossover tube is removed they are to be replaced. On Common Rail ISB's they are a one time use piece. They are roughly 6-8 bucks a piece and have been updated 2 or 3times.