The following is at this site in the "DIY Article" section:
http://www.peachparts.com/Wikka/M103ValveSeals
Covers the inline, 12 valve, straight-6 motor
You can also use the SEARCH facility, looking for things like "Valve stem seal" and "titles only". A lot has been written on this.
http://www.peachparts.com/shopforum/search.php?searchid=742815
Tech manuals available at:
http://mb.braingears.com/