Many times the rotor will come right off by hitting on it with a soft hammer from behind while rotating it.
If it doesn't...
Break the big nut lose with the tires on the ground but leave it tight. Jack the side you are working on high to keep differential fluid from running out. Remove wheel and brake caliper. Caliper takes a 3/8" allan head.
Remove three of the four bolts that hold the unit bearing on from the back side, they take a 12 point socket. Leave the last bolt most of the way screwed out, wedge a socket with extension in-between the bolt and differential housing, start the engine and turn the steering wheel to pop the bearing off. You will hear it very clearly when it pops. Leaving the big nut tight prevents the bearing form busting apart.
During this process keep the axle in it's normal position by stuffing rags under the u-joint. This keeps the axle seal from deforming and possibly leaking.
When you have the rotor off pound the studs out with a copper or brass headed hammer or press.
Pound the studs into the new rotor using a drift then make sure they are pulled in tight by tightening down a lug nut with a pile of washers under it.
Coat the axle stub with anti-seize before putting the bearing/rotor back on so it comes off easy next time.
Joe. . I just banged them out and put then back on. New ones are a good idea too but here's how I did mine:tell him he has to remove the wheel studs as they hold the rotor to the hub (on the 99 for sure) so he may want to pick up some new studs unless he has a shre fire way of removaly without damaging them . . .
When you get the Hubs off the knuckle the Hub and rotor are together as an assembly. To seperate them put the Hub/Rotor assembly on the floor on two 2x4's. Get a hammer and put a nut on a stud a few threads to protect the bolt and wack it fast with the 3 lb sledge. They will pop out pretty easy once you get the hang of it. I re-used all the studs.
Now the hub is seperated from rotor. Get the new rotor (remember to get the correct right or left side if using drilled or slotted rotors) and tap the studs back in. I re-inserted the nuts and tightened a little to seat the studs and then removed the nuts. Put the hub rotor assembly back into the cleaned and anti-seized knuckle.
Last time I did my front brakes I did everything except I re-used the same old studs, and I used a nut and impact to pull the studs back in on the new rotors instead of pressing them in. Well, either they were tight holes in the new rotors or I somehow got some of the splines on the studs off in the rotor holes, because I buggered up 80% of those studs by over-tensioning the threads trying to pull them into those new rotors. Now one of these days I've got to pull it apart again and replace them. They're working fine for now, I just wish I didn't reuse those same old OEM studs that were a bit worn in the threads to begin with. Might be food for thought.