I built an amp similar to the stereo Model G (
K502 from AES) as my very first DIY project some years ago, and I think it's as good as anything else for a first project. It's very easy to put together and I think it took me all of four or five hours from start to finish.
One positive is that lots of people have built these amps, made modifications, and posted online. So, if you find out you like doing this kind of stuff, there's plenty to keep you busy until you move on to bigger and better projects.
From a sonic perspective, it sounds pretty good. But for <$200 it's not the greatest thing ever -- it's niche is as a decent-sounding 'first' kit. Also, if you have any DIY amp experience then I'd think you wouldn't find it particularly interesting.
Regards,
John