Hi All

Looking at purchasing either GPSMAP 451 or 551 Chartplotter.
I currently have a GPSMAP 178C combochartplotter/sounder with external GPS antenna. This unit is 5 years old and the screen has started to fail. Gradually loosing the picture and am wanting to upgrade.
I recently installed a Furuno FCV620 sounder so only need a chartplotter. Require some assistance with following:

1. Unit will be mounted inside the aluminium console onboat which is covered over top and rear of unit. Will the internal antenna on the 451/551 work in this arrangement? My thought is that it will not but someone may have come across a similar issue.
If not, can I use my existing GPS antenna? Not sure what it is as I cant pick up a If not, what external antenna is compatiblewith the 451?

2. What cables/connections do I require to connectto Furuno FCV 620 Echo Sounder? I am a complete newby with all this NMEA stuff but am I right in the understanding that this sounder can talk to the GPS and vice versa?

3. What is the best compatible software for mapping onPC? On Apple?

4. I have over 5 years of waypoints, saved tracks and odometer data on the old 178C. Can I transfer this to the new 451/551 unit? Pretty sure I can do the waypoints but not sure about the odometer data.

Thanks in advance.