After some work and changing hosting providers, I successfully loaded, launched and wizarded my way through MT 4.23. Then I downloaded the Motion Upgrade and read through the install guide and it said “UNZIP”. As simple as that?
So I FTP’d the MT-4.25b1-en zip file to my server and then SSH logged in to unzip it on my webserver. I thought it happened automatically, but no. I then had more success when I renamed file folders, but kept both installations separate. I have cg-bin files with directory named MT 4.23 and MT and my new MT Folder has Motion files in it. I also have html folder with mt-static 4.23 and mt-static with motion in.
So are these files supposed to be combined? Or do I delete the MT 4.23 files? My FTP program won’t allow me to move files because they are named the same. Any help?
Reported on Movable Type 4.2

You do realize that Motion is a beta release, and intended for testing, not daily use, right?
To answer your question, you should have no problem if you copy all of the contents of the motion installation over your previous installation. It's just an upgrade that adds some new components. Just unzip it then do cp -R MT-4.25b1-en/* existing_mt_install/
Hi Mike! Yes, I do understand, please forgive my overt enthusiasm. I think Motion is the best platform on our planet right now. What I did was move all my 4.23 files to a new folder I created above cgi-bin and html folders. Then I did a new installation wizard and went through the steps again. When I completed, the last step did a database upgrade. So far it works well. Will I run into any complications by doing it this way?
Two other quick things-
No box in upper right for users.
When I write a post, no option to add audio, video, etc.
I do have the right version now installed it says:
Movable Type Pro version 4.25b1-en with: Community Pack 1.62, Professional Pack 1.21 at bottom.
I am not using Motion, so I can't help you on this part, but WRT your first question, you should be fine. Hopefully, you backed up your database before going through with this.
Just an important update. I downloaded the MT-4.25b1-en and installed it on 5 domains successfully. I got good at this!