re: sales tax on labor, yay or nay?

The short answer is it depends on the service you are providing. Every state has different definitions of a "service" and what is exempt from sales tax. It seems that in the state of Louisiana repair of movable objects (in your case appliances) are subject to a sales tax. This is a straight forward question that a CPA knowledgeable in the subject or the Dept. of Rev could answer for you pretty easily.

An example of the different codes is roofers in La and Tx. In Tx roofers are not considered the end users of the materials (i.e shingles) so they are issued a resale certificate and do not pay tax on those materials. Therefore they must charge tax on the service they provide. In La the opposite is true. The roofer pays tax on the shingles because they are the end user and their service is sales tax exempt to the client having the roofing job done.