I replaced the PCM with a used one on a 1999 Chrysler Concord and was able to write the VIN. Yours maybe different. That year I think you will only be able to update calibrations.
 http://tinyurl.com/hme3fa2

 there are a few ways to change vin in the pcm depending on the year,make and model. now keeping in mind it reads the vin from the skim/wcm all you need to do is unplug the skim or wcm then go to pcm/special function or misc function and read/change vin, connect your skim/wcm back and start vehicle. this does not work on newer vehicles with win module/node. the correct way to do it is by going to skim/wcm/win then misc function or special function then click on replace pcm, pin code is needed though if done this way, on new vehicles with win node is the only way unless you have abrites commander or similar hack tools. good luck.

 on this old car what you have to do is simple. try this. go to pcm/ special function/vin read change. right before you click on vin read, turn key off and wait for the prompt invalid vin then turn key on, write vin, cycle key and start.