First, welcome to the forum.
Next, the help zone link is in the big yellow banner at the top of this page, or, for your question, you can go
here.
Next, with so few kilometers, how often has the oil been changed and what oil is being used? Old oil breaks down and causes lifter noise, which, by the way, isn't normal for the 5.3L power plant.
As with older oil, the wrong viscosity oil will also cause excessive noise. For example, in the summer months I use a 10W oil and the winter sees 5W. Either way, that noise is not normal and if you still have warranty left on your truck, then force the issue and make sure someone else performs the diagnosis.
Hope that helps.
Mac