WOW!!!! They were really going to take me to the cleaners for this!!! I got a callback this evening and the estimate they quoted me was $540!!! Allegedly, they couldn't get just the cover and new ring without ordering the whole servo/piston package, the parts just didn't come separately. So they wanted the go-ahead to replace the whole unit!
SHENANEGANS!!!! I called St. Charles and spoke to Merlin (the man!). I simply asked him what parts were neccessary to fix the leaking accumulator piston cover.... $10 worth of parts!!! I went ahead and ordered the stuff (it was the least I could do) and took my case to the service dept at Isuzu. In so many words I told them there's no 'right or wrong' to their repair recommendation, but let's call a spade a spade; I did not need a new $540 servo! I said this is the way I want you to repair it (per [St. Charles'] standard procedure), and they were more than happy to oblige. Damn straight!
Buyer beware!!!! Being an informed consumer saved me some $400, and I would have been a sucker if not for this community. It kills me how they insisted there was no other (cheaper) way to fix it.... well they were in for a suprise; momma didn't raise no fool! I'm sure labor ($90/hr) could be found cheaper elsewhere too, but at this point I was content to set an example. Besides, this dealership is right around the corner from me and it'd be a shame if I ever did need something serious, I'd have to go miles to find the next closest one. In short, thanks for everyone's concern.
These are the part #s in case anyone else needs 'em:
Snap ring: 8-96015-714-0
Cover: 8-96017-093-0
BTW: Although they admitted it looked like it could've been leaking for an indeterminate amount of time, there was no chance at letting it slide under any warranty coverage. I dunno how far out it was but I'm at 52K miles and the (original) in-serve date was Dec 2000. Your guess is as good as mine when it comes to warranty coverage for non-original owners.
Cheers!