Vice grips will 9 times out of 10 slip and round off the bolt. As far as the fork itself goes I normally use channel locks and WD-40 and I have never seen one I can't break free with a little bit of grunt. Do you have the stem and handlebars out of it yet? If all that doesn't work try to get some kind of heat to it. A propane torch works great for that.
For the fender bolt make sure you have the right screwdriver tip that fits it snugly, WD-40 the snot out of it, and if you can't get it then use a grinder and remove it and use a self tapping screw for the fender. :mrgreen: