Suspension Fork Maintenance

Hi I recently took the bike to the shop so that a new crankset will be installed 😎 The guy asked me about the maintenance I do to my fork, I said it works perfectly and has no leaks so leave it as it is. It is around a year old. When I pick the bike up the guy said to me that those forks are very good and tough (it is a Marzocchi MX Comp w/ETA) if they are well maintained and advice and offered his service.
I took it home and give it a ride, then last Sunday I decided to change it's oil, Since I didn't want to mess to much with the fork (since it is working nicely) I just took the upper caps (screwed), turned it upside down, drain the oil on a vessel, measure how much oil it drained and the replaced the oil with Yamahas suspension oil (grade 15).
Is what I did O.K? Should I use other type of oil? Should I do something else as periodic maintenance besides cleaning it and change oil? Drained oil looked clean, on the air filled leg was a little like lather. Any recommendation will be greatly appreciated.