Volkswagen Repair: Poor performance, mass airflow sensor, vw dealership

Question
I recently had my 2001 VW Beetle (turbocharged diesel) worked on at a VW dealership.  My bill was $1827!  I actually told them not to fix some things, thinking I could fix them myself.  They replaced the glowplug harness, relay, and glowplugs.  They also replaced the mass airflow sensor.  They told me the intake manifold was caked with carbon, and would cost $275 to clean and replace the gasket.  I told them not to do it, I thought maybe I could.
Now win you really accelerate the motor shuts completely down, just like you shut the key off, then it starts back up.  Elapsed time about 1 second.  Is the car going to quit me? Or should I just keep my foot out of it?  Where can I find a manual to help me get this fixed?

Answer
First Off, how soon did this problem happen after you got the car back?  Take it back.  They got to fix that if they screwed it up. For 1827 it seems really high for the little work that they did...((just as an example here in Canada, where everything costs more  GlowPlugs25 ea relay55harness50maybe mass airflow sensor I don't got but will guess 125 so, being on the generous side  lets say 400(for ease of figuring) on parts.  Time to put in the plugs for them I don't expect longer than 45min, harness15 is high, relay2 mass airflow10 So, lets say be generous and say 2 hours.    So, at $700.00 hr they gave you a broken vehicle.  Like, you know you should be a little irate.   Thing is, you arn't the first one that I have heard some rather ridiculous numbers.

You have a 3 year old car with carbon build up?  Did you ask them what do they figure is the reason for that?   Mine is 20 years old with 300K and got no such thing.

UNDERSTAND The carbon has nothing to do with it shutting off.  They would be lying if they said so.
     Uh, the harness and glowplugs(while you could have done it yourself)it is a pain to do requiring a knack of fiddling with the tips of your fingers(provided you got smallish hands) and alot of patience.  I never like doing them, the relay did it need it?... well, I think they do it as a safety precaution so it is one thing that you can rule out if there is a problem.  The mass airflow sensor...now I have been so lucky as not to have that toy yet whatever it is and does.  So I can't help you there.
 The story with diesels is this.....diesels either run or they don't. Once you got them started and they got a continous supply of fuel,you can't shut them off.  In a gas vehicle, if the altenator is removed and the battery taken away, short out the coil, wreck the spark plug wires, or damage the plugs or the distributor your car shuts off.
     In a diesel, power is required for the starter to turn the motor over and for the glow plugs to "glo" when the motor is cold(like first thing in the morning)  AND power is required to keep open a shut off valve which cuts off the fuel(to shut the motor down).  
  The battery is needed to keep the flow of fuel going even gravity fed systems.   If it is dying, I would look at your diesel fuel injection pump for the operation of the cut-off solenoid.  If you look on the top of it near the fuel injector line end, but on top, you will see a single thin wire that is held down by a small nut(8mm).  That is your cut-off solenoid.  Is that connection good is the wire good etc.  Move it around, (the wire), pull on it, whatever.     Now take off the nut so that you can remove the wire.  Suspend the end so it doesn't touch anything for a moment. Now turn on the ignition dash lights.  Go back to the solenoid and with that wire touch the place it is suppose to go.  Can you hear a click noise.  Will only be 1 when you touch.  Solenoid is working fine.  Check that wire condition.  If all is good make sure the end is clean(use sandpaper ) and reconnect.  You can do the intake manifold provided you get the car up on ramps, because you have to do work from the underside.  It'll be greasy, and sooty and stuff like that but you can do it.  If you wanna go the manual route, Library is a good place to start --doesn't even have to be a bug could be a jetta or Rabbit  Haynes is a good publication...but take a few different ones and maybe they fill each other MT spots or have different pics that would help.
  There is also 1 vacuum hose that runs from the turbo to the top of the injection pump...make sure that is tight.
  Get up and go is not so great in the winter months as diesel fuel is more kerosene that diesel(to keep the fuel from gelling in the lines) and the energy value of kero is lower than diesel.  Something else to keep in mind.