OK. Firstly don't start looking things up on the internet. There really is a lot of rubbish out there.
Secondly, keep calm, Remember Lynne Faulds Wood? OK this you can look up: www.bowelcancer.tv/cgi-bin/page.pl it is all about bowel cancer.
Go with your dad to see the specialist. Write down what you want to ask and take your time. As them to spell everyting out in laymans terms and if you don't understand, ask them to say it again.
Ask what the treatment/s is/are. What are the pros and cons of each. Who will be doing it and where?
What can you do now to help dad through this? Diet, exercise... what shouldn't he do?
What should you be looking out for in the meantime (pains, temperature, whatever).
My friend's dad had the same and after he was better he went on some weird diet from a nutritionist to keep the bowels and colon healthy. Yes, it sounded weird but made sense to him (no tomatoes, grain, etc).
Think of the future. I know you will be terrified and I am sure dad will be puting on a brave face but you will get through this.
Yes, cancer is a complete bastard. It really is a hard road, but you need to be positive and keep a clear head.
Be strong and I will be sending out positive vibes for a good prognosis.