… Steam locomotives being my passion so building a working model would be my ambition.
Welcome John. I advise starting with something simpler than a locomotive. Although LBSC, and others, produced plans for simple locos, they’re still a challenge.
I found Stewart Hart’s PottyMill engine a good starter project. Fabricated, no castings. Run on compressed air – no need for a boiler. Difficult enough to stretch learning whilst not too hard or years of work.

Or maybe a simple oscillating engine.
There’s a lot to learn about tools, techniques, materials, how long jobs take, and what might go wrong. Some people learn best by jumping in the deep end. I prefer to master the basics and build on them.
Enjoy – it’s a fantastic hobby.
Dave