TDI engines have always been scare and expensive.  With the price of gas the
last couple of years, the situation is even worse.  Many VW owners are
swapping them into their cars.  It is extremely difficult to find a complete
engine for less than 3-4K, and then they usually have high miles.  A TDI
conversion, even done independently, is extremely expensive unless you
happen upon a great local "find" of an engine.  And then regearing your
transmission is pretty much required if you want to go over 60 on the highway.

John