Not knowing what difference there is in the two models I'd take both apart and mark the parts that go with each other. Putting the knives back together isn't hard. I've done it several times to install scales I've made.
Here is the video I watched before doing anything to a Manix2.
http://www.youtube.com/watch?v=7c_9vtjda3o
Don't take the scales off the lanyard tube if you don't need to. I think during assemble the lanyard tube is expanded to make the scales fit VERY tight. If you want to swap blades only it's best NOT to remove the scales so they stay as snug around the lanyard tube as possible. It's ok if you do take them off, I have. I just think it's better to leave the scales on the tube if you can.
I made notes and typed the following steps to go by the next time I may need to take one apart.
MANIX2 ASSEMBLY STEPS
At this point the knife is dis-assembled and the liners and scales are still on the lanyard tube. The scales and liners are laying as if the blade were pointing to the right and the edge at the bottom. Top liner and scale are swung out of the way. NOTE: Use blue loc-tite if you want to.
Put bushing on liner and the pivot pin on top of it and line up the D shape in the liner. Hold it in place by screwing the pivot screw in on the bottom scale. Don’t tighten screw, just snug it up.
Install back bar with back screw only.
Put in buttons/ball/spring assembly. Hold them in place and push the front of the back bar down and install front screw in back bar.
Pull the buttons back with left hand. Holding blade pointing up slightly, place it over the pivot and lower it until it drops into place in front of the back bar.
Place second bushing on blade over pivot.
Swing top liner and scale to position them. Install the 2 back bar screws and pivot screw.
Tighten all screws. Adjust pivot if needed.
Hope this helps. Pay attention to how the lock works while you have it taken apart. I got a greater appreciation for it's strength after understanding exactly how it works by looking at it.
Jack