Repairing and testing is always give and take. You replaced the Diode, OK. You want to test it, maybe it will work? Go ahead. If it works, replace C34? That's on you at that point. Do you have a spare C34 to throw in there? If you do I would say yes but you don't have too.

I have always thought that diode replacement was to remove the old one and replace with 2 (smaller signal) diodes in series with each other.