http://www.peachparts.com/shopforum/showthread.php?threadid=28059
This is but one; there are MANY to be found using SEARCH. Be sure to buy the CD for the M103 motor as well. I believe they sell it at this site.
I would also do a SEARCH for valve stem seal replacement. Lots of good head work info in some of those posts as well.
And last, but not least, there's a "DIY Links" forums here with all sorts of information.