Re: Champ(ish) build
Seriously... if you think about a tube amp as an arc welder you plug a guitar into then you're in the right mindset for the safety side of things.
That being said, a champ or something vaguely similar (such as a MOD 201 or AX84) is a great place to start for dabbling/building tube amplifiers. Tons of great resources out there, tried and tested schematics etc, etc.