paid subscription mod for syncing to other products

[CydeSwype]

Sorry if this has been discussed before but I couldn't find anything pertinent from the search.

I'm integrating vbulleting with phpfox and phlymail. There's a notion of a paid membership and I create a mail account and upgrade the user in phpfox upon upgrading to paid membership. I have two problems:

1. which hook should I be using to know when the payment is complete via PayPal (the IVN service should let me know when the transaction is complete, but I can't figure out what the corresponding hook is so I can put my code in as a hook).

2. what hook (if any) is available for when the user decides to cancel their membership? I see a hook titled paidsub_delete but I'm not sure where that gets invoked. In fact, I don't see where the user can even cancel their subscription on the frontend. Can someone point me to that also?

For extra credit, I've seen some posts saying that no hook is available if a user cancels their sub through paypal directly, as apparently the IVN service doesn't offer a call back to the client's site upon cancellation? Can someone verify that? That seems like a real flaw in IVN. Have to research that.

Thanks!
-Ian