I'm comfortable doing basic computer upgrades and maintenance - installing and replacing drives, fans, memory, etc.. - but haven't wielded a soldering iron in twenty years. And wasn't very good at it when I did. So I'm wondering if the upgrade will be something that can be accomplished with some screwdrivers and careful dis/reassembly, or something more involved?
Congratulations on your Batch One Baby Jet and Upgrade Kit.
You will find installing the second mini-board to be a quick and easy process.
The procedure is as simple as mounting the mini-board on case's risers, hooking up the second cooling unit, and swapping out the original PSU for the more powerful one. Then connect the USB cable to the Raspberry Pi controller and you're done!
All you need is a screwdriver and a beer, as depicted below:
The beer is actually optional, but highly recommended. You may also use a sonic screwdriver, if available in your galaxy and/or timeline!