Haven't done it personally but here's a "How-to" for a 2JZ-GTE which is same procedure as a 1JZ-GTE.
http://www.mkiv.com/techarticles/valve_stem/index.html
90913-02089 / 90913-02090 for exhaust / intake valve stem seals ; quoted @ $6.90 each from Penrith Toyota.
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