Hi acato
Welcome to the forum.. am sure you will get all your queries answered here...
on the cisco site you have a tab called products & Solutions, which would have datasheets of all wan, routing and switching products and modules.. I would advice you to have a look at this, and let us know specific questions you have.. as a starting point u can visit the following url:
http://www.cisco.com/en/US/products/hw/routers/index.html
if you go into a router model , say 3800, you will find the chassis datasheet and info about relevant modules which can fit inside this router.
Hope this helps.. all the best..
Raj