I would not mess with injectors until there was some complaint which suggests they need work...

However, concerning the glowplugs, the TRiCK to getting them out of aluminum heads is that they needed to have been installed with antiseize compound on the threads.. so that really is a TRiCK after the fact...
But it brings up something in terms of philosophy... if these guys are correct in that they will probably not be a problem removing at this number of miles or years on the car... and you plan on KEEPING the car... then it might make sense to pull them and INSTALL Antiseize compound on them NOW....