Unfortunately, that 16 valve b234 was not Volvo's best effort. It runs strong, but not many see your 180,000 miles. If you like the car otherwise, you might want to think about just finding a good, used standard 8 valve replacement. That way, you would still have your a/c compressor, etc. All things being equal, I would not spend $3000 to rebuild the b234. Of course, the problem may not be as serious as you think. If a second opinion is more hopeful, then just be sure you change your timing belt every 50k, and drive it.