Terry, I do not think a camera is going to give you the full picture (so to speak) of the condition of your exhaust connectors. The best and safest way to do this job, is by dissasembly and visual inspection. The bad part is that these connectors are often on there pretty tight, in which case it is better to cut them off rather than risk damage to the exhaust pipes. A frend of mine has a 1980 45 TF with 6V92TA's in it. He just went through replacing both long fiberglass pipes that lead from the engine room to the muffler. (You are right, the water tank has to be removed.) His were cracked. Remember, one hell of a lot of water goes through those pipes. If there is a failure? Well, you get the picture. While you are down there, check the exhaust side of the turbos to make sure they are spinning freely and have no evidence of water damage.
As for the exhaust, I found on another forum (Boatdiesel.com) that a guy replaced the mufflers on his 671TIB,s with new Veritones. He reported that it reduced the sound level pretty much and did not have any effect on his engines.