Trying to replace a belt on STX-30 John Deere Lawn tractor. Manual
lost or misplaced. Involves 4 pulleys, arranged elleptically. No one
seems to know right configuration to arrange belts on pulleys. Can you
help?

Here is the source for manuals on the John Deere web site.  They have
a parts catalog to order the belt, as well as the owners manual, both
available for purchase.  I could not find any online documents that
illustrate what you need to see.
Here's how you get to the manuals:
http://www.johndeere.com
select "USA/Canada"
select "farmers, ranchers" "farm site" "enter farm site" in the center
green column
Under "service and support" go to "publications and manuals"
Select "locate, purchase and view manuals online"
type "STX30" into the search window

You will see both the 1989 and 1990 model versions of the manuals. 
Unfortunately, these publications are NOT viewable online, only
available for purchase in hard copy.  They cost $14.20, and I would
imagine have a drawing of the belt configuration.