Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.
I've played around with the PIC18F2550 using modified MicroChip code. Trust me, it is way easier to hack their C code than try and write your own USB code. If you are not intimately familiar with the USB spec, then learning C from scratch will be easier.
You could download their code, compile it, and then look at the dissassebly listing if you really wanna see it in assembly.