I just did mine last weekend, Its easiest to do both, as you will have everything apart anyways.
Its a 36MM socket to get the hub nut off, and it might be just the right size to be able to push your old seals out, and new seals in. I used a combination of the socket, and a custom sized washer (took the minigrinder to a large washer).
I would probably start soaking the 3 bolts on the back side holding the hub on with PB Blast before you start, they arent impossible to take off, but PB blast should make it a little easier.
A writeup also:
Go to -
http://www.madxj.com ->Technical
-> Axles
-> Front Axle Seals and Upgrading to 297-X U-Joints (dont worry about the 297-X U-joints)