The first thing to consider is that the capacity of the replacement silencer should be adequate to contain the backflow of water from the exhaust pipe when the engine is switched off, and you have considered this.
The second thing is that is that there should be space for the new silencer and you have also considered this.
When I changed the silencer in my 30 Classic, I had to use a similar one to the original, due limitations of space. I found no hidden or unforseen difficulties. It was just a matter of taking out the old one, cleaning up the space and installing the new one, making sure that all the hose clips were properly tightened, etc.