Be VERY CAREFULL removing pulley, if it has THREE holes around metal inner part use them (if neccessary), they will either come off easy or be a sod to do.
Seal is easy to get out with SCREW AND PLIERS , just screw into the seal with a screw and pull with pliers!!, you will most likely have to wrok it around the circumference but it will come out.
Make sure that you put sealant on new seal outer edge, very small amount and oil the inner lip.
Have a close look at cam seals too while there, might be worth replacing anyway ?
Front crank seal same as aux shaft 42-56-7, about £3 each.
DO NOT UNDER ANY CIRCUMSTANCES LEVER ON THE OUTER BONDED EDGE, as these are prone to coming off and you are into a new pulley then.
tabetha