you can add a state (Configuration > Asset Pages > Asset States > Add Asset State) , call it 'Retired' (I use the term Decommissioned)... go to main assets page, choose your assets, mass edit the 'state' field, set to 'Retired'.
Then you can filter the main assets page by state = 'Retired', and export to excel.
Store the Excel file somewhere, and then filter assets page again by 'Retired', select all of those,and 'delete asset'
if you want more info on the assets, you can make a different report (Or edit reports - example 'software: List of software by computer' - join tblstate table, filter on state = 'retired') but doing stuff like that would take a bit of time.