First thing you have to determine is which monitor you have in your RFM. It will be either a WG -Wells Gardner or a Ducksan. Everything I have read indicates the WG is the better of the two as far as reliability, but both will benefit from the addition of the video amp.
The pictures posted by Alveolus & Nibbles are for wiring the WG monitor. The Ducksan is a little more difficult & requires you to cut a trace on the Ultimarc amp p.c.b. to separate the vertical & horizontal sync. There are many posts showing how to hook up this monitor too.
One other important tip would be to be sure to turn down the brightness & contrast pots on the board behind the translite before you turn the pin on. Once you install the amp and everything is working you can re-adjust these two controls to your liking.
I don't know of anyone currently selling Nucore. "Pinball Life" shows it on there website but it is not available currently.
Good luck this amp is very worth while, you won't believe the difference in the display !