I did the same. Took a multi year break from owning fish ( but still worked in the fish industry) and now have another fish hatchery going.
You'll find that things have changed a bit from 40 years ago ( I was there then so I know
) but the old basics still ring true. Not everything new is necessary or even better. It's just different.
As long as you were successful in the past, you can be again.
I will say this however, today's fish are not up to the standards of the fish from the past. There is a lot of junk out there so be very particular in what you buy. Not all fish today can be saved due to their genetic weakness'. ( I see this in the fish I breed.
) Also, be prepared to quarantine every new fish you get as there are many diseases now that weren't around in the past and the meds that used to fix them aren't all available anymore either.
Now that I have probably bummed you out,
Welcome back to fish keeping.