Some data on 450d shutter life:
http://www.olegkikin.com/shutterlife/canon_eos450d.htm
I've never tried it but this says it will check the count:
http://astrojargon.net/%28X%281%29S%...9/EOSInfo.aspx
And if you're on a mac:
http://astrojargon.net/%28X%281%29S%...ookieSupport=1
I know someone who got their 5d shutter repaired and it cost him about $200, not sure about a 450d though.