If you don't know when the timing belt has last been changed, then of course you should change it on ANY of the VW diesels. Just to add my own data point to the mix, my '02 jetta wagon just passed 240,000 miles and runs flawlessly.
If you don't know when the timing belt has been changed on any timing belt engine, you should change it if there is any visible wear and it is possibly past the original service interval.