Install louvered vent with flashing behind hardie plank

I need to install a louvered vent VP528 into side of my house. The vent includes a square box protruding into wall where I can insert 8" round pipe (to vent-a-hood). It also has 1.5" surround flashing that installs against sheeting under the siding. Here are pictures: http://ventahoodparts.weebly.com/uploads/1/4/0/1/14017120/247697_orig.jpg http://s1.img-b.com/ventingdirect.com/imagebase/resized/220x220/vent-a-hoodimages/VP538-2.jpg What is best way to cut square into hardie plank siding and how do I get surround flashing installed under it? Any special steps to caulk or weather proof this? I would like to make this as clean and unobtrusive as possible (very visible area of house for a very large vent).