Book value of RRSP vs Contributions

[Confused]

I'm back with a new question on how to report RRSP in the US. I had a RRSP back in Canada since 2004. I collapsed it on Jan. 10 2011, 6 days after I became a US resident. I don't have all the information necessary to determine the book value of my RRSP the day I became a resident. I do know the total of my contributions since the beginning. If I use the total distributions on the CRA slip minus my contributions for the "taxable part" would it be ok?
I know that it's not the real book value, but the financial institution that held my RRSP cannot help me with the book value.
I do not care if I pay a little bit more taxes that what I should. On that topic, is the total of the contributions usually less than the book value?

Any help would be appreciated.