Change oil and filter
Inspect this and inspect that and charge you for the labor
You didn't say what year or engine you have but if you have the latest gen with the 3.5L V6 the plug change interval is 120,000 miles which is a good thing. You have to take the top of the engine off to get to the back 3 plugs...
2008 Highlander Limited AWD, Silver, SmartKey, VSC/TRAK, Bluetooth, Remote Start, No Nav, Tow package/hitch/color matched fascia, roof rack cross rails, Color keyed mud guards, Camry trumpet horns