I have a laundry hookup I assume is similar to this:
https://www.google.com/search?q=laun...8AidC3S1ZZM8M:

The drain is blocked so we have been draining the washer out the
window to keep from opening up the wall to replace the drain section.

Well now one of the water valves is leaking so it seems like a good
time to fix both problems. I called a plumber and told him what I
needed and he said because of all the busted pipes that he could come
out and replace the valves (so I can turn the water back on to the
house), but the drain would have to be later.

So can he replace the water valves and then come back and shoe in the
drain? I guess my question is can the trim piece be put in after
doing the plumbing or does the drain, water, and trim piece have to go
in together.