I think you only owe $330 as that was the rent payable at the time it was missed.

Also you're obviously a relatively long term tenant, therefore given that fact, and the fact that they took sooo long to pick it up, they should have no issues agreeing to a repayment plan over the next couple of months.

I'd suggest you write an email / letter to the agent stating what you will pay and when; they are more likely to agree if they have it in writing.