John -- I was in the same position. I had never updated an ardunio. But the benefits of KD8CEC's stuff was utterly compelling. So off the cliff I went. The "use case" for me was:
I was inept at the push button menu system in the stock firmware and yearned for a PC-type interface.
I wanted a bigger nextion screen (which is totally dreamy by the way)
Most of all I wanted to run wsjtx and fldigi, and CAT control was required for the digital mode operation.
To load the CEC firmware, you do not use memory manger. You use a little app that burns/updates/replaces/etc. the firmware into the aruduio. For folks who work with aruduio's and the like, this is second nature. Totally natural like cream in the coffee. For the rest of us. it is a total freak out. You put the CEC firmware into the ubitx with a usb cable between the laptop and the min usb port on the arudio, and then use a tool like XLoader.exe to do the burn/update/replacement. I was 100% sure I would destroy my beloved uBIX and create unfathomable and unrecoverable errors. But it worked fine after I solved the usual windows com port challenges.
AFter XLoader has run and done the update, then tools like memory manager give you the pc like interface to the ubix. Which is a revelation. All the internal ubitx parameters are VERY easy to see and update. At last.
Good luck and have fun.