For the first part of your question; There is a fair bit of instruction within these build diaries. You get posts from members with rudimentary skills all the way up to pro luthiers. Time would be well spent here. YouTube, of course, is another great resource. Parts rarely fit together straight from the factory so some amount of fitting is involved when buying loaded bodies and neck sub assemblies.
For the second part; You can start out simple with a kit. I did this and learned a lot from the process. It will almost certainly give you a thirst for more. From there you can go as far as your ambition takes you given access to good timber and tools, either hand or machine. There's plenty of scope for creativity. It's not quite like Meccano but, as mentioned in the first part, it is possible to get playable results from off the shelf items with a little bit of fettling.
I wish you a lot of joy with it.