The new device should indicate its own attributes only. It is not recommended to use the same Name. The old asset should either go back to stock awaiting disposal or go for repair based on the scenario and the processes which you have defined. It is important that the 'State' and 'Substate' fields of both the old and new assets automatically get updated to indicate appropriate values as part of the replacement process.

Are you using HAM pro? Then you should look at the OOB asset lifecycle flows and make modified copies of those flows to address your requirements. The 'State' and 'Substate' updates happen automatically as part of these flows. Refer the following links about a couple of lifecycle flows which involve asset replacement:

https://docs.servicenow.com/bundle/washingtondc-it-asset-management/page/product/hardware-asset-mana...

https://docs.servicenow.com/bundle/washingtondc-it-asset-management/page/product/hardware-asset-mana...