@Walt296
You control what is on the invocie or sales receipt by selecting the items you charge the customer for.
Create the service items for labor and what ever services you perform that you charge for
If you stock parts that is inventory type items
if you buy what you need for the repair use a non inventory type item, on the item screen check mark that it is used in an assembly or for resale, and fill in the purchase and sales side. Use that item on both the purchase and the sale
You can "sell" inventory items for a zero sales price if they are included in the service, like oil for an oil change service. Listing the item at a zero sales price will cause the cost of the item to post to expense (COGS or another expense account depending on your item set up) and if it is an inventory item, qty on hand will go down.
