More info on my previous post.
Curiosity got the better of me. I scrolled through boatdiesel's articles on repowering and found the date of the link referenced above. 12/1/04. So add 17 yrs inflation to the costs in the article.
Also this link from 6/17/05.
Repowering a 34 foot Californian. Another DIY project with used engines this time. This will give you a better picture of what's involved in repowering your Californian with respect to getting things out and in. This author brought the project in at $9,000. So if you're willing to go with used gear and DIY then it can be quite affordable.
Regarding DIY working on boats isn't rocket surgery. But experience helps a lot. And taking the time to research and plan every aspect of a major project before diving in. Avoid the allyougottadois monster.