It's a tough spot. Even if you pay all that dough, it still could take a while. You're just trying to get other opinions in order to make a prudent decision. Do you have a place and desire to work on it yourself?
1. The car is used? Can you talk to the previous owner about what was done to the car. Just because it's not in the vw database, doesn't mean it was not done.
2. Can you ask the dealer that did the diagnosis for an analysis of why exactly they say the pump is shot? Maybe including a printout of the diagnostic computer. They really should have this if they're going to make such a drastic recommendation as this.
3. Perhaps another VW dealer's opinion could be obtained. Tell them ahead of time you're very interested in seeing any computer printouts and analyses of results, since you'll be paying for this.
4. It is indeed possible to look at a diagnostic computer, (either VW's or the $200 vag-com program that runs on a laptop) to see if the pump is injecting fuel within permissable limits, and if the two electronic components relating to injection quantity control and measurement are within specification.
5. You are living on borrowed time if the timing belt wasn't changed yet.
6. If they made a mis-diagnosis, something fixable, (by you), could be the problem. It might be a good sign that there was no check engine or glow plug light.
7. As far as what else could be wrong, if they totally blew the diagnosis:
a. I don't know what other conditions could cause the revs to increase like that without any pedal. Maybe the accelerator potentiometer is messed up. Anyone else?
b. As far as loss of power goes, you need to check the complete air flow path and also the fuel path. So new filters and clearing any clogged screens and possible soot accumulation in the intake.
c. You need to get someone with a diagnosis computer to check things too. There's a whole list of things in the Bentley CD, that one could go down, like fuel flow, air flow, boost pressure, timing, etc at idle and at full throttle.