I hope to be able to make something that nice some day. My sewing clothes skills are still in the 'elastic band A-like skirt' level. Not that there is anything wrong with a good skirt, but a coat like that is way out of my league. I'm so impressed.
This coat is my first one and before that I only sewed cotton summer dresses or skirt. I think you have to have faith in you skill and follow the pattern. Go the the thrift shop buy some cheap bed linen and used them as muslin for the pattern you want to try that way you can make all the mistake on it.
I'm a bit of a fearless craftster, when I learned to knit, my second project had ribbing, cables and a side way braid, all thing that experience knitter would tackle but not beginners, the result was great I'm really proud of it! My philosophy : if you eat it, try it! In the end, it's only fabric and thread or yarn