Well, here is the latest.
All the grills (which constitute most of the front end) are going to have to be replaced, since they have no hope of getting the stuff off of their unfinished textured surfaces. The front bumper is also going to be removed in order to be able to clean out the radiator, inter-cooler and condenser fins. They're reserving judgment on the paint until they see if they have any luck removing the goo. The turn-signal lenses on the mirrors may well have to be replaced, too.
The kicker is that this stuff has a tendency to etch glass, and it's done just that. So the GTI is going to be getting a new windscreen to boot. I forgot to mention them to the shop, but the HID headlamps (as well as the fogs) have glass housings so they need to be checked for etching as well. You don't want to know what a set of HIDs go for...
All the replacement parts are going to be OE Volkswagen. At this point, with just the grills, the windscreen and a detail job, it's easily into four figures. If it needs any other trim or a set of lenses, much less paint or a set of fogs or headlamps, we're talking some really serious money.
The fun has just barely begun.