If working with an old connector, the pins are fairly
difficult to get out.
There is a tool to do it, AMP part 455822-2. Mouser lists it as $22 but
cms-tools.com lists it at $14. On most RS232 pins you can push them out the
back with needlenose pliers if you're careful instead of using a tool. That
approach doesn't work on the MR connectors, so may have to get the tool. I'm
experimenting with a RS232 pin tool to see if it will depress the MR
connector pin locks correctly.
If that doesn't work, you may want to look at hobby-shop thinwall
brass tubing to fabricate your own tool. It's quite inexpensive and
the brass is easy to work. The operative magic incantation is "K&S
tubing".