Not Too Bad
It realy isn't that hard to do. Just like previous responses, get an electricians snake, drill a hole at the base of the mast (make sure you put in a rubber gromet so the chafe doesn't cut the coax cable) Drill another hole at the mast head (about 6" down from the top) run the snake from the top down and then tape the wire to the snake. At the top finish it off with a "clam shell ventalator" by perko marine they come in different sizes so pick the right size to cover the hole and then silicone it up. At the base of the mast use a rubber grommet and silicone that in as well. Then find a thru-deck connecter for your cabin top cable connection (waterproof)so you can easily disconnect the cable when you take your mast up and down, and silicone that as well. The rest inside the cabin is cosmetics. Make sure the antenna is a high as possible as VHF is a line-of-site sound wave and does not travel well over obstacles. If you only want weather (as the coast guard can now triangulate your position using a cell phone signal) then take it back and trade it in for a hand held, much easier. Good Luck