[Vwdiesel] Timing belt - job done -- NEW question about injectors

[Craig Osborn]

A while ago I reported a squeal and loss of vacuum assist w / oil light --
 
Here is the final "report".
I changed the timing belt and tensioner.
1- I found melted rubber deposits on the tensioner pulley, so I guess that
the bearing was about to fail.  I dodged a bullet on this one!
2- I also noticed that the vacuum pump was loose and water could indeed
enter the system explaining the lockup of the intermediate shaft (someone
guessed that water may have entered the vacuum system and ice would cause
the lockup in cold temps). 
3- There was a small crack in the fuel line between the pump and filter that
was letting in air bubbles. 
After fixing all three of these items, the truck runs again without any
incidents of squealing or loss of vacuum assist/ oil pressure.
I will still need to fine tune my injection pump timing as it is harder to
start in cold weather than it used to be before the repair.
 
I am also planning to replace the glow plugs with the fast ones and service
the injectors.
 
Question -- new injectors are fairly expensive.  I see that injector nozzles
are available at a reasonable price.  Can I get as good a result by
inserting a new nozzle in my existing injectors as I could by replacing the
entire injector with a new or rebuilt injector?  Is the job of rebuilding an
injector difficult?   
 
Craig