Help with imported data

[Tech Account]

Howdy, I have our customers in Freeside now, but I do have a problem...
We are in the middle of a billing cycle, and I have payments from the
past which I need to post, as well as importing the current status
of payments into the accounts.  Once that is done, I have to run a 
clean billing cycle and verify that the invoices which are generated
are correct.  Is there an easy way to do this?  Can I enter in owed
amounts and payments in a batch mode?
How do I make freeside think someone owes money?  What if this amount
is more or less than the amount of the current packages for that
user?  There must be some way to handle this, I can't imagine everyone
using the system started out using it....

Please advise...code examples would be nice, but I'll take whatever
I can get!

-techy