GPS/Fishfinder Install-Jupiter FL Vicinity?

[SeekingStripers]

I am considering upgrading a very old and out of date GPS unit (Lowrance Global Map 2000) as the sonar no longer is responding. I also have an older but functioning Raymarine fishfinder (DX400 or something like that). Can anyone recommend a local party that would be able to assist with the install of a new unit? Can this be done while the boat is in the water? I am not sure if the new units could use the old wiring or transponders. I am considering calling a few local marinas and determining their capabilities as I am sure they can assist but thought I would post the question here first.

Thanks for any input as always.