you need a puller to remove the pulley, then you pry the old seal out and tap the new one back in. you can rent pullers at many parts stores. here is some links and videos from a google search. power steering pulley remover - Google Search re-install it using the same tool, do not hammer the pulley back on you can damage the pump. you might do better buying a whole rebuild kit and re-sealing the whole thing while you have it out, or buying a new one they aren't to expensive around $45.
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