Long 6mm allen socket, Hand 3/8" drive impact, and a fork seal installer. You can use a piece of PVC pipe in place of the installer. (Get one that fits close)
Procedure:
remove leg, turn upside down and remove 6mm allen from bottom of leg using hand impact. Drain fluid.
depending on softail model there may be a collar at the top of the leg. FL softails just have a clip on top of the seal. Remove the clip.
Hold the upper leg in one hand lower in the other and expand leg hard against the seal. It will take a few wacks but the seal and upper leg will come out of the lower. Watch for the damper rod end cap. It sometimes stay with the upper and others remains in the lower. Be prepared for a mess of oil as it all does not drain out from the first step.
Remove old seal from leg. Clean upper and lower. Be sure damper rod end cap is in place and Reinstall upper leg into lower and reinstall 6mm bolt. place a light coat of fork fluid on inner edge of seal and slide it onto the upper fork leg as far as possible. Using fork seal installer or suitable PVC pipe slide it down the leg onto the seal. Use it like a slide hammer to drive the seal down until you can reistall the retainer clip. Fill with required amount of oil and re-install the leg.
Good luck and you have my number if you need it.