Step 3: Making Everything Fit (aka The Tricky Part)
There isn't a lot of room inside the phaser. Since all the mechanical parts still have to work, it's going to be a tight fit. Start with the laser module - use a dremel with a grinder to make a cavity.
The cylinder shape is pretty much the exact size of the laser module, and makes quick work out of plastic. Clean up the edges, and make sure the module fits. Glue it in place on one half of the phaser.
While you have the glue out, start gluing down the mess of wires, and the battery holder.
Make sure you don't have any short circuits along the way. You can glue down the laser driver circuit if you like, but I won't recommend it. It's much easier to remove and replace if something breaks, and the driver is a good spot to start troubleshooting. Once everything is in place, replace all the mechanical parts.
There's a couple of springs that can get frustrating - just be patient, and it will all come together. Once the two halves of the phaser toy are back together, replace the screws, and reattach the type 1 phaser. You now have a working (hopefully burning) phaser!
If you like things pretty, or somehow lost the thrill of burning things with light, you can glue the broken piece from Step 1 and replace it. Just remember that once you do that, you'll have to break it again when it comes time to change the battery.
Voila! Your very own outer space peacemaker.