If you like this kind of thing, just go in and give it a shot! The NES is a great place to start, just three registers and simple instruction set. The display unit ABI is well documented and there's a couple of NES debuggers out there.

Starting with no experience, I wrote a program to dump level images straight from a ROM:

https://gitlab.com/mcmapper/mcmapper/blob/master/main.c

https://tcrf.net/Proto:M.C._Kids