These older Colt's require two special tools to disassemble.
Try it without the tools and you'll ruin the ejector and these are factory fitted parts. You can't just buy a used one and expect it to fit. The ejector sets head space and barrel/cylinder gap among other things, and if you damage the original, you're in real trouble.
Even with the tools there is a risk of damaging the assembly.
To disassemble;
Make or buy a special ejector wrench. This is a piece of flat steel about 1/8" thick which is cut out in the center to fit snuggly down over the ratchet in the end of the ejector.
If you're willing to take a big chance of ruining the ejector, some people have used sockets from a socket that will fit over the ratchet snuggly.
Put three EMPTY cartridge cases in the cylinder and put the ejector rod head in a padded vise.
Grip the cylinder and unscrew the ejector from the checkered ejector rod head.
Remove the empty caaes.
Using the wrench, lift the ejector from the cylinder slightly and VERY CAREFULLY unscrew the ejector from the ejector rod. The ejector is RIGHT HAND theads.
Slide the cylinder off the ejector and crane assembly.
Using a special tube wrench, unscrew the ejector bushing from the rear of the crane barrel.
Slide the ejector and spring out of the crane barrel.
You can buy the wrench from Brownell's for small to medium Colt's but I don't know if it will fit the larger New Service.
http://www.brownells.com/.aspx/pid=712/Product/COLT_CRANE_BUSHING_TOOL
To reassemble, reverse the process, but be EXTREMELY careful when you start the ejector back onto the ejector rod. These are very easy to cross thread, and if you do, you've ruined it.
Screw the ejector back on slowly until you feel it's getting tight, then turn it far enough for the witness mark and the holes in the ejector to line up with the pins in the cylinder.
Make sure the ejector is fully on and bottoms into the cylinder.
