Perfectly ok, I have done it many times. A quick peek will tell you a lot. If my
engine overheats and I pull off the cover of the raw seawater
pump and find a damaged impeller with a broken or missing impeller blade, I first replace the impeller and then pull off the inlet side of the
heat exchanger. That is usually where the broken blade resides. If the tubes are all calcified , it is no big deal to pull the tube out and do a gentle acid/water
cleaning and replace. At this point, I would replace the O- rings.
Working on your
diesel is not that hard, get some metric tools, a good manual and watch some You Tube videos. You will be a better and more confident
boat owner.