There is a lot of info on CCO, eg:
http://cisco.com/en/US/products/sw/iosswrel/ps1834/products_feature_guide09186a00800e9760.html
My personal suggestion: make sure that:
1. you use a very recent image. Like 12.4(11)T1.
2. your telco has made extremely clear to you what are the configuration parameters they expect, and are willing to collaborate.
3. that in the worst case, you are entitled to open a case with Cisco TAC.
E1/R2 is not like ISDN where when things don't work are easy to diagnose and fix. It is a legacy signaling protocol with his own quirks and requires technicians to have a solid understanding of the way it works.
