A monrg ago I had, continued....

If it drives, then it is driveable. if the turbo is leaking exhaust, it is not necessarily dead, but it is likely not functioning up to it's potential, but it depends how severe the leak is. The bigger the leak, the less drive the turbo has to spin itself up. The vehicle can function just fine indefinitely w/ a completely non-functioning turbo. The turbo is a really cool device, but it's about as essential as your floormats. As far as the price goes, does that $2000 include a new turbo? If so, is that really necessary? if it's just the turbo's gasket leaking you should be able to get away w/ just a gasket to fix the leak. A turbo can be a messy replacement if it is needed as it is the single hottest component in the whole car (it actually glows red when it's working hard since the turbine can spin up to 140,000 rpm). Anything that gets that hot tends to degrade the bolts and nuts that hold it in place over time. If you do decide to do this, keep in mind that there is a matching turbo on the front bank of that motor that is the same age and could potentially be near having the same problem. As far as the O2 sensor goes, it increases your gas mileage by making your engine run more efficiently. O2 sensors go bad over time, and if you're not seeing blue oil smoke coming out of the tailpipe, i wouldn't worry too much about the oil-contamination issue.