Little help hooking up a pbx

Hello, I thought i would simply build a pbx system using my small business Comcast line. However i have found this is not simple.
my goal was to take a server running Asterisk and plug a phone line and create a sip server. I have spent allot of time researching this and have confused my self with FXO lines and sip truning and other stuff.
If anyone has experience with this please help me with terminology and any tips you have.
or even if this is possible
Thank you

I can give you some help, Please start asking questions …

Is it possible to use phone line (rj-11) instead of a sip

I thought your issue was bigger, Yes you can do it using Digium Analog Card, Read the following link … 97307.html

Thank you very much that link helped allot
From what i read that card is different from just your rj-11 port on the back of your pc. it has a framework built in to control all the feature telephone lines have like caller id and controlling dial tones and such.
I could be wrong im not an expert on phone lines