I didn’t think it would be that simple!
go to this link:
https://www.codeproject.com/Articles/18399/Localizing-System-MessageBox
Download the source. Take the MessageBoxManager.cs file, add it to your project. Now just register it once in your code (for example in the Main() method inside your Program.cs file) and it will work every time you call MessageBox.Show():
MessageBoxManager.OK = "Alright";
MessageBoxManager.Yes = "Yep!";
MessageBoxManager.No = "Nope";
MessageBoxManager.Register();
See this answer for the source code here for MessageBoxManager.cs.