I changed my analog Raytheon/JRC radar on my 1999 MS350 to a Simrad radar. I had to remove the mast by removing the large Phillips head screws around the base and cutting through the sealant. I think it was 5200 and I had to get some solvent designed specifically for 5200. This was a slow process Pulling the old cable out of the mast was the easy part. There was a large hose similar to the water hoses used on boats that ran from the base of the mast forward to the bump in the fly bridge helm that was used as a conduit. I had to use a lot of wire pulling lubricant to pull the old cable out and the new one through and it wasn't easy. I probably had to remove the old connector to do this. Fortunately the new cable was a thinner Ethernet like cable.
On our current boat I went with the wireless Raymarine radar, Quantum 2. It is nice in that you only have to run power and ground to it, no data cable. Makes it much easier to run since no connectors.