Does the migration required any user-side action?
I had a seed of ARK wallet written somewhere - should I perform any action, or my funds will be still accessible with this old seed?
Nothing needs to be done from user, user shouldn't experience any difference when interacting with Ark blockchain all of this happened in the "back" with the ones who are running the network (delegates).
Are you sure that there is no action at all required? You should at least have to download another wallet or something, don't you?