It's straightforward in a conceptual sense, but as with most things there are a ton of gotchas and fiddly implementation details, especially if you're doing it in your kitchen/garage. A lot of the difficulty comes with the tedium of maintaining sterile conditions and lots and lots of pipetting.

If you're really interested in DIYBIO there are subreddits and many tuts out there, but fair warning: getting started is easy, but the devil is in the details a heck of a lot more than learning to code.