It can’t be too hard because there will be step by step instructions that come with the kit.
Option #2 APC-80
Well, just following the instructions and printing that PDF doesn’t seem too hard and an APC 40 and an APC 20 cost up to only about $375 together so it won’t really break the bank.
Just gonna take a bunch of cheap gear the performs well and try and just put them all together in a case and have a usb hub and sound card hidden inside it somewhere. Not the most reasonable but it is the easiest.
My advice is to start small.
Order a midifighter classic and expand it with 4 extra buttons and faders.
You will get all the tutorial you need from this forum.
Practice soldering by opening up crappy/broken gear and desolder components and solder wires were the components used to go.
I built a custom midicontroller this way in under 2 months not knowing anything about soldering from the start.
Theres tons of good tutorials on soldering on youtube.