Boat upholstery is the easiest thing you will ever tackle. If you are comfortable with an industrial sewing machine, you have 90% of what you need to do what you want to do. If you are not comfortable with the machine, sew simple things (straight, flat seams) until you are not afraid of the sewing machine. An industrial machine goes 5 times faster than a home sewing machine, so it takes a lot of experience to get to a comfort level.
You can't learn to do upholstery work from a book. You need to learn, hands on, while running the sewing machine, preferably from someone who knows what they are doing. Given that that isn't going to happen, this is my advise.
The problem most beginners have is assuming what they take apart, and make patterns from, is perfect, and don't know if it is perfect or not. The reality is ( especially with boat upholstery) is that what you take apart was produced on an assembly line and sewed together by people who are paid on incentive by how many pieces they can sew together the fastest, and by people who cut the material and don't care how close they cut to the pattern lines because they are paid the same way.
Learn how to use the sewing machine first, and then start your project.
No one lives forever, the trick is creating something that will.