I'm about changing pending status to completed status.
I read http://www.ubercart.org/docs/developer/920/order_states_and_statuses
When a customer completes checkout, the order gets moved from the default in_checkout status to the default status for the post_checkout state. (By default, this is "Pending.")

1) So I think default status pending is correct. Am I right ?
2) I want changing status to complete automatic.

I don't understand meaning of "Update order status on full payment" in workflow and it's disabled by default.

I setup my workflow:
event: Customer completes checkout
Conditions: Check the order balance - Balance is greater than $0.00.
actions: Update the order status - order: completed

but after payments status order is still pending...
I'm lost.