GPS Antenna wires
I have seen several different types of GPS antennas on the Garmin units.
I had a older Garmin that did use a coax cable. These are probably the easiest to cut and splice. Use a male and a female connector or just replace the connector at one end.
The antenna on my Garmin 3006C is a GPS17 or GPS17x that is wired into the antenna on one end and has to be connected to the NMEA183 interface of the GPS. Three wires for signal plus power and ground. I use a euro terminal strip (Radio Shack) for the connections.
I just installed a Garmin 4210 over the weekend. That ships with a GPS17x with a NMEA2000 interface. This setup is a lot more involved just to hook the antenna up. Three T-connectors, two terminators, one cable for power and one cable to the GPS17x. I pulled it with the connector on. Not sure of the feeds and speeds of this type of network connection but splicing into a eurostrip would probably be fine. Keep the pairs twisted together right up to the eurostrip on both sides.
I just posted a picture of my new setup and my wiring board.
http://www.greatgrady.com/forum/viewtopic.php?t=9296