tapping into Vaillant Ebus data

I am completely clueless software wise, these days, but 40 years ago I could manage to get by....
A few years ago, with a lot of help, I somehow managed to muddle through set up a Rpi, to log my weather stations data, which it still continues to do, to this day. It appears as neat values, and graphs, as a series of webpages, in cumulusmx. That, from vague memory, is a Rpi 3 B.
I now want to tap into the ebus data, of my Vaillant heating system, and control system. Towards this end, I have ordered a ebus, to wifi adaptor. One of these - https://www.elecrow.com/ebus-to-wifi-adapter-module-v5-2.html
I'm fine with setting that up, configuring it to my LAN etc., just struggling with the next steps...
It's been suggested I need a second Rpi, dedicated to the data collection from the ebus, something about installing ebusd on it, to translate the data, plus some higher level system, to display and collate the data? Home Assistant, or similar, but I don't need anything fancy, or difficult to set up, and many experts seem to struggle.
Which of the many Rpi models do I need for this, what memory, and what sdcard please?
Anyone able to explain to an idiot, and in simple terms, how to set it all up?
A usefull extra, would be what I think might be called a mini-NAS. Just a USB stick plugged into one of the Rpi's, able to store files, accessible to any PC on my network..