You went from 10 to 9? Odd choice but ok.

Depending on BCD (bolt circle diameter) you should be able to swap chainrings though sometimes shifting might change as well? Some set ups might have issues shifting and some chainrings don't always play nice together but it generally is possible. However I will say sometimes it is cheaper to get a new crankset than buy all new chainrings.

It is easy enough to do on your own but you will need a chainring nut spanner for most stuff simply because a lot of crank manufacturers still cling to those old nuts instead of using hex bolts on both sides. However Wolf Tooth Components makes excellent crank bolts that are dual sided hex, made in the USA and come in some cool colors. I haven't fully installed them yet but tested them out on an old XT crank (with Biopacé chainrings for age reference) for the outer and middle cranks and they will work just fine (for double) the inner already uses a hex bolt and won't be seen.