Engine whirring noise after water pump, timing belt and accessory belt replacement

After having the above-mentioned repairs done the engine makes a whirring noise. The mechanic who did the work said it is normal because the belt is new but he is the only one who thinks that. I took it to a Chrysler dealer who said it is most likely the timing belt tension-er but the only way to know for sure is to remove the new accessory belts and see if the noise is still there. He said it would take sixty to ninety minutes to do this but if the tension-er needed to be adjusted that would mean a lot more labor time. After watching your PT Cruiser squealing belt on start-up common fix how to where you replaced the tension-er I am wondering if it could also be adjusted using your method. Could you let me know if you agree with the dealer's suggested fix or what you would do in this case? If that is too many questions, would you please just let me know how much time it took to replace the tension-er? Thank you very much in advance. Lou