Looks like a really nice kit. Heyboer are quality transformers. If you don't already have them, you'll need a pair of long needle-nose pliers and a side-cutter that'll let you snip off soldered wires down close to the board. A digital multimeter will come in handy as well. Sorting out all the parts and identifying all the resistor values before you start will save you a lot of time. A 25w soldering pencil is likely all you'll need.
Expect something less than stellar tubes to come with it. (I notice they don't specify what brand you're getting.) Upgrading the tubes is likely the easiest way to improve the sound, should it need improvement.
Please try not to electrocute yourself.
Document your build with pictures along the way, and keep us informed. Have fun building it.