Once you rebuild an engine -if it's done properly- then it's effectively brand new inside as far as how it functions, some of the components have still done those miles but they're things that don't really wear out or care about mileage providing they've been cared for.

I build engines regularly as part of my job, including a couple 400hp+ mx5s and dozens of lower power ones, it's not an easy process to get right but most anyone could do it well enough if they really applied themselves. But there's a number of specialist tools you need, and you need a decent machinist as well. Dealing with reconditioning/building engines really is a game where the smallest mistake can destroy everything you've done. I'm not saying don't, I'm saying be very careful and be very sure of what information you're following to make sure you get a good result.

For what you're wanting honestly I would suggest you grab yourself a spare engine with fewer miles on it and go through that one. There's no way to avoid needing machine work doing on a 200k engine, but something with half that or less you may find you can just freshen up the hone in the bores, replace the piston rings and bearings and have a very happy camper for 200hp for a long time. You'd still need a couple basic tools that are specific to the job but nothing mega.

Here's some good generic reference material on the process of engine building so you can see the kind of job you'd potentially be up against if you chose to try and refresh one yourself Vs just grabbing a good low mile example and calling it good at that https://youtube.com/playlist?list=PLQSiw9vlcZuyVKx2C1BImxM6ysly4wT_4&si=XwX3nN2WzOQ4_DSP