What to check after years of disuse?

I haven't used my OG V1 modded switch in 5+ years, what steps do I need to take to check updates, cfw, any new must haves for installing, etc?

I want to start running modded Mario odyssey, but want to keep everything intact (i.e able to run sysnand online.) I vaguely remember hekate, atmosphere, backing up the sysnand (Not sure if i still have it) and maybe a dns block? Unsure about an emunand, but its likely.

Completely lost on where to start though, any help is appreciated!