Klt, I think there are two warning sounds, one is overheat and one low oil are you sure its the low oil ? V6s don't like running at tickover for long.
Two things I would check and both are quite easy. Compression test the engine which takes about 10 minutes even if a dealer has to do it and if you think there is a heat problem then off with the gearbox and check the water pump.
From memory the compression should be about 120 - 125 psi in good condition, if any are really more than 10 - 15% you have a problem but those are quite tough engines and have been around along time so ppl know how to fix them and spares are available. I ran one with 120 - 110 - 115 on one bank for a year without too much drama it just overheated at slow speeds after a while.