With some time and patience, you can learn it all yourself. Buy a Chilton or Haynes at your local auto store and read, read, read - as you go. Before buying all of the above (buy the book), maybe do a quick once over to the engine and ensure it is worth spending the cash on those parts beforehand. Some service literature for our trucks:
http://67-72chevytrucks.com/vboard/s...d.php?t=558016