I'd recommend watching The Ben Heck Show on YouTube. It features two pinball builds from scratch. He features electronics builds and can give you a great start. Also review the builds here in the Homebrew section. Lastly, I'd recommend reviewing the restoration sections. Lots of detail on hardware and cabinets so you can understand their construction.

Good luck.

It is more expensive to create a game from scratch than to buy it new. That said, you don't have to buy it all at once and with time and effort you can get there.

http://poormanspinball.blogspot.com/2012/08/to-baldly-go-where-no-ones-gone-before.html is one of my favorite examples of how it can spiral out of control but worth the effort. The Ben Heck Show also reinforces this point. Even if you have the tools, the parts, electronics, and materials do add up quickly.

To those saying, don't do it and you can't. We were all neophites at one point. I don't see the need to knock a total stranger down for an idea. I'm sure once they get introduced to the topic with some direction they can decide if its still for them.

I will add though Rudi. You came to pinside and appear to have posted without much effort into researching the idea before you ask questions. Maybe, take advantage of the search features and do some research. You can learn a lot both about the machine and process your interested in, and the community.