@Clean Install:
The mod has its own installer, it does not use FLMM anymore.
Using a clean install is incredibly advised. I mean more advised than a President would be.
I say this mostly due to the server's anti-cheat. It won't be nice to you if things are wrong.
De-activating 4.85, restoring backups and then installing 4.86 may work. It may not.
Using a clean install is your best bet.
If you do not have your CD anymore, it is legal in most countries to download a copy of the game as you already own it. You will find a copy floating around the internet if you look for it, even using Google will work.
Alternatively, ask someone on skype to help you out.
@Pre-post 4.86 equipment de-mounting.
Best to do it before 4.86. This ensures you both: A)Don't forget and B)Don't log in while in space with a broken loadout, try to shoot and crash your game