I tinted my rear ext. cab windows and back windows with Limo Tint (5%) over the factory tint so its at 3% total, I love that set up myself. VERY Dark, your going to have to get used to using your side mirrors at night. I'm going 35% on the front side windows when I get around to it, I'd go darker on the sides but your asking for trouble in MN with any darker. 35% is still illegal, but generally they don't hassle you unless its super dark. Law states that you are not allowed darker then 50% on any window here in Minnesota, but rear and rear side windows they don't hassle over, now front windows are a different story. I wouldn't advise having the windshield done if its your DD, if its a show car or Sunday afternoon cruiser then go for it but I wouldn't want the windshield very dark for night driving in a DD.
Also make sure who ever you have tint your windows knows what they are doing, I can't count the number of "Tint Jobs" I've seen done with tint from walmart or a parts store that you can tell the installation and/or material was terrible from 50 feet away. Make sure to use 3M, llumar, SolarGuard, etc. All of these are GOOD brands, that will last forever if applied correctly