here is a start I made:

install drupal
create content
enable modules
per http://www.ubercart.org/docs/user/8075/installing_ubercart
enable core required first
token, token actions. core ubercart modules
optional: file downloads, reports, payment, paypal
per http://www.ubercart.org/docs/user/8387/drupal_settings_tips
uncheck box that makes new account require email verification
admin/user/permissions
download files anan auth
crearte order
view own order, payments

admin/store/settings/checkout/edit
login users

admin/store/settings/checkout/edit/panes
uncheck customer info, delivery, billy, comments

admin/store/settings/cart/edit/block

dmin/store/settings/payment/edit/methods
put in paypal address sandbox vendor,
check show debug

admin/store/settings/products/edit/fields
uncheck image
admin/store/settings/products/edit/features
make dir and put ../files_example

admin/store/settings/reports
pick all report statuses

admin/store/settings/store/edit
store name, owner, email address

create content product
make a product.
put text in, sku, sell price: 3.33
uncheck shippable

node/2/edit/features
edit node, pick features
put file in directory, or have it already there. start typing the name
pick a sku on: 10001
go to home page

log out
anonymous
add to cart
checkout

does not work , order is created, but account is not created (log says cannot send email... like it doesnt get the email address from paypal)

create user
order goes through, but
no file in files tab
and order status is paypal pending
log says
IPN transaction verified. but... paypal order status stays at pending