Automate Invoice & Purchase order?

Automate Invoice & Purchase order?

Hi,

I run a company that brokers a service and charges customers up front on the net. I use a gateway called eWay from my site. 

It would be good if I could automate an email as soon as a stage is changed (ie from lead --> Closed/Won) - and when the invoice is raised a purchase order is automatically raised to a vendor who we broker the services from.

Is this possible?