is the cam still on the head?
if the valves were recently adjusted, but not driven much after, they could still leak if they are good. I would remove the springs and visually inspect the valves for grooves and cracks/burns and such. valve lapping compound is affordable, and pretty simple to do, if no cracks or burns are evident.
spring pressure should hold back fluid if the valves are good.
http://www.v6z24.com/howto/valvelapping
http://www.powrgrip.com/cgi-bin/powrgrip/V1275.html
http://www.goodson.com/store/template/product_display.php?NID=61
here is a link to a forum discussion of valves/ and lapping etc...
http://cartalk.com/board/showthreaded.php?Cat=0&Number=328489&page=0&vc=1