Crack's been my first DIY kitbuild. I learned to solder by building Crack.
Thanks to the superb manual, even with skill-level 0, Crack is a safe bet.
Be confident, you can build it.
For the money, and how it taught me a lot about how audio, tubes and stuff works (all, that standard, of the shelf stuff didn't) it is probably the best amplifier i ever bought and ever will buy.
Compared to many (more expensive) amps the last few years, i can say with confidence that the Crack is indeed a gaint-killer with Sennheiser HD6xx/HD800 headphones.
The journey, building it, enjoying it, modding it, enjoying it further is what makes the Crack special. Don't miss out on that, build one yourself.