Welacome.
You will find lots of help on here if you need it.
I agree with Noel, a Big Boy in any scale seems overambitious for anyone returning to the hobby.
You might end up being frustrated and disillusioned, before completion.
It would be better to become familiar with your machines and materials and gradually work up to something as ambitious as a locomotive, especially an articulated!
Walk before trying to sprint!
Howard