I'm assuming that you're going to give them a new, unique part number.
 
I would do it through IN-C. The only complication I can think of is that the Average Cost on the original part number may not accurately reflect the real cost (if you have a bunch of different parts with the same part number). In that case, first go into IN-K and change the Average Cost. Go back after you're done and change it to what the new Average should be without the parts you just took out.

If you are adding inventory through IN-C, the General Ledger transaction should be a plus$ to "R" type inventory account and a minus $ to your Production Supply Expense account, however, you will probably need to edit the GL account for these IN-C transactions  to your Production Supply Expense account in GL-P, because DBA has a default account for all transactions processed via IN-C, which is usually to Cost of Goods Sold.

The GL account that is expensed ( as well as the asset account that is debited) is controlled by the class code for the item.  The item type doesn't matter. An N type can be debited to an asset account when purchased if it has that in its class code.  This can create havoc if you are comparing your GL asset total to your Inventory value which doesn't give N types any value.
When you make your new part number, give it a new class code or temporarily change the class code you want to use -- change the COGS account to the expense account you have been using for the N type.  When you do an adjustment to the new part, DBA will credit the expense account and debit your RM asset account.  Then change the COGS for the class code back to what it should be for RM.
 
PS YOu don't need to do anything to the N type since DBA doesn't keep track of how many there are or what the average cost is.  All N type parts have presumably been expensed and don't count and so you don't count them either!