I have a 1989 780, but Im sort of confused about what it is mechanically (perhaps you can help?). It appears to have a water cooled turbo (lines running to the coolant system) and it does not (as far as I can tell) have a "k block" engine. Is this possibly a late model year quirk with my car?

If I do wind up replacing the turbo, how feasable is it for me to do the work myself? It looks relatively simple if I find a unit that can be swapped. Also, how can I determine the swapability of a unit? Looking on Ebay theres a few which look pretty nice and definately are more in my price range than I was expecting. Lots of them say they are garret T3's but it also seems theres some subtle differences between turbos, the meaning of which I dont really understand (this car is my first experience working on a turbo engine).