I just replaced my engine in November. I had 62,000 miles and it went. Cost to replace the motor is $5,000. It took about 1 week for the engine to come in and a couple of days to install. Talk your dealer into giving you a loaner at no expense, that's the least they can do since the motor is flawed from Isuzu. They know it but never did anything about it.
If you are the first owner, the 2000 model you have is still under powertrain warranty. If you are the second owner, you will have to foot the bill on your own because Isuzu won't pay.