Yes, like the vast majority of dual-cab utes sold in Australia, the Holden Rodeo was indeed built in Thailand, at the Isuzu plant (the Rodeo was an Isuzu D-Max under the skin apart from the petrol V6 version which used a Holden-made engine). But diesel Rodeos used the Isuzu 4JJ1 four-cylinder diesel which used a timing chain rather than a rubber toothed timing belt. As such, the chain should be good for the life of the engine.

If the engine were reconditioned by a reputable engine reconditioning company and they gave you a guarantee with it you can be confident that it will last a long time. How long is impossible to say. There would be little difference between the exchange reconditioned engine and the one done by your mechanic. Either way you should check on what they are going to do the engine in the reconditioning process, so you can be confident that it is done professionally and properly.

Everything has a statutory guarantee with it that covers the goods as sold. That you installed the engine yourself shouldn’t have any bearing on the guarantee, unless it can be shown that you have done something to cause the fault. In your case it would seem that is not the situation and the problem is with the engine as supplied by Holden.