A 2.4 diesel can easily be converted to TD, I've done it. There are tons of parts available for doing turbo swaps. Some things like manifolds you can get from the Volvo TDI 5-cylinder engines sold in Europe. Other things like injection pumps you can get from an Audi 2.0 TD engine. The 2.4s even have oil squirters and whatnot.
But, as has been mentioned, it will be a lot more work than swapping in a 4-cylinder. Depending on the transmission, you won't need a new one, but you will need a different bellhousing to mate to the 5-cyl. The motor carrier bars aren't that expensive. ZSI has a bunch of them. But the alternator/PS pump/AC pump/clutch and whatnot, I think, would be the real turn off. VW put 5 cylinder engines the their South African transporters, so if you could get all of those parts, it probably wouldn't be too bad.
There's also lots of thread on thesamba.com about doing diesel swaps and/or 5-cylinder swaps into these vehicles. IIRC Audi V6 and V8 swaps are even possible. (Gotta have that bellhousing though.)