Replace one side of a tank?

[WindowMaker]

Hi all, I have a 55 that as per usual is tempered all the way around. I would like to change this and replace it with a non tempered piece. My question is how easily can this be done? I would assume I pull the top and bottom trim off, cut out the old piece, clean the edges of old silicone then do the opposite to stick the new one in. What kind of thickness should I be looking at for this 48x12x18 tank? Is there a particular silicone that is recommended?

thanks in advance!