Sales tax is charged on parts, etc. not labor.

This depends on how you complete your invoices that you give to your customers. For instance, if you list one amount for repair of a computer, then you will have to pay sales tax on the entire amount. If you list parts and labor separately on your invoices, then you will be liable for sale tax only on the amount of the parts and not for labor. Your parts amount will be required to reflect your cost for the parts plus an amount for profit and handling of the parts. If you try to get cute and bill for $1 on parts and $100 for labor on a repair that had parts, they will disallow the separation so you have to be truthful on your billing and it is expected that the parts amount will be more than your cost for the parts.

Parts and labor about $350.00.

$250-300 parts and labor

Standard labor time, without complete transfer of parts, is 5.1 hours. With complete transfer of parts, it's 5.7 hours.