How hard is it to change a u joint on the front axle of a 1998 dodge 1/2 ton standard cab pick up?

They are not hard to replace as long as you have the right tools. One thing I will warn you about is the wheel bearing. Usually the axle nut that holds the axle in the wheel bearing is torqued to 400+ ft/lbs and is a ^$%26amp;*( to get loose and you may wind up breaking tools. Other than that, they aren't bad.