Some of the "basic" marine systems are easier to deal with. The newer NEMA networks seem more, rather than less, complicated.

Most of the more sophisticated systems seem to run on their own proprietary system (Raymarine, B&G, Simrad, etc) plus having been ported for one or both of the NEMA standards. If you follow the manual CAREFULLY, you can probably make a discrete system work. The more sophisticated systems intra-device buses are much faster, plus if you don't use them, you lose functionality

(There are rather obscure intracasies or tricks. For example: B&G requires that you put a shunt at end of "branches", or else you get intermittent false signals which affects an autopilot linked to the system. I found this out after months of frustrating errors -- and one miserable spinnaker wrap. THe shunt at the end of the "chain" hadn't been reinstalled after being disconnected. A little "plug-in" fixed the problems instantly.)

Having "helped" professionals doing work on our boat myself, there are cases where I was productive, productive, or just "along for the ride". It depends on the task(s) at hand, the skill required, etc. Even the act of running wires through the boat, labling them properly, doing it in a workmanlike fashion, and avoiding electro magnetic interference seems simple enough, but isn't.

I've known people that have done this work themselves and NOT had any issues; but that less often than not. When it was just a simple Data Marine "Speedo", "Windmachine", and Depthsounder (about three decades ago), it was a lot more likely. :^)))