I have a motorola i830 nextel cell phone and would like to use an unlocked motorola razr on the nextel network, using my sim presumably. would this work? is there anything i could do to get this to work? thanks

hey wzup  did you ever find out about using a a nextel sim card on a unlocked razor.

Unfortunately no.  Razr is for CDMA or GSM service, Nextel service requires Nextel sim, and is not compatible in any way.  
Hope that answers the question, and you can pm me for further help.