If you've decided on the Prusa, it is a good idea to read thoroughly the assembly pages on his web site, which occasionally include videos. This will help you beyond the printed manual, as the web pages are more up-to-date than the printed material. Paper printing, not 3D printing!

Also, there are many Prusa-authored videos on YouTube which will be of value, not only to Prusa owners, but some are useful to any 3D printer owner.

For software, you have a huge selection. Stay away from SketchUp for creating 3D models to be printed. You can find many instances on the 'net of people who have designed models with that program and have had problems getting them to print properly.

On the plus side, you can use TinkerCad, which is simplistic and somewhat limiting. OnShape is less limiting, more challenging to learn, fairly powerful and capable. Even more challenging would be Autodesk's Fusion 360, which is free for hobbyist use and requires that you re-license once per year. I've used all of the above, as well as Meshmixer, which is handy for checking model integrity and for measuring completed parts. I like the plane cut feature for cutting difficult models for better printing. For more esoteric users, OpenSCAD is a text-based modeling program that can be written for parametric design, a feature at the top of my happy-3D-printing list. Another "off-the-wall" program that engages my interest is SolveSpace, another parametric 3D modeling package that approaches the build in a unique manner, but with similar aspects to many of the other programs.

All of the above programs are free to download and install. OnShape is browser based, no download required.

When you engage your brain cells, you'll have plenty more questions. Use The Google first to see if you can find an answer that you can understand. From there, this forum and the 3D printing Stack Exchange are good resources for your questions. This forum is less strict than the Stack Exchange, so if you join there, read carefully the rules and recommendations.

For your tutorials, use The Google again, or your favorite search engine and type as the search terms the name of the program and the word tutorial. Many many results for all of the above!

Good luck!