Converting that part is pretty straight forward. Pbp has a serout command also, the manual can point you to the syntax for it. I think there may be a section addressing some of the differences between the stamp and using pbp with pic's.

The hardest part is you have total control now over all aspects of the uP. What this means is you will have to get intimate with the datasheet for getting all the registers set correctly. Pay close attention to how to set up the ports for digital and how to get your osc running.

So go read up on that stuff and try to write the program. Post what you get and we will all jump in to help you get it working AND understand why it does.