I just did this on a '98. I bought a replacement bumper from Auto Parts Warehouse for $113.30.
If you are rusted, soak all the bolts with WD40 or similar in advance.
1.
Take out the two turn signal lights & unplug the connectors. You'll see two bolts that hold the bumper inboard of the where each lights were. They can be accessed from below too. Remove those.
2. There is also one bolt on each far end side of the bumper. remover those too. These might be tough if they are rusted. Patience rules.
this will allow you to remove the bumper & the attached plastic piece below, all as one unit.
If you are keeping the plastic piece below the steel bumper, there are 8 fasteners that are probably rusted worse than the bolts holding the bumper. replace these 8 with some short bolts/washer/nuts you pick up at the hardware store and bolt them to the new bumper while it is off the truck.
Reinstall is reverse. Spray some WD40 in the light sockets & plug in the lights again.
Probably a 2 hour job depending how rusted the fasteners are.