Hi there, and welcome to the forum.
I'm not a tug man myself but I do know that many people have built them as an introduction to the hobby.
I assume you're going electric as opposed to IC or steam ? My initial advice would be to read the instructions twice over and try to match the kit contents to the instructions….before starting work.
No, it's not too early to be thinking about colours especially if you want a scale-looking craft / working boat etc.
Usually, further questions will fall out as you progress – motors, radio, props, rudders and the various control linkages etc. Just ask away there will be a tug expert somewhere on here to help.
Happy modelling,
Dave