I am replacing a hood with an over the range microwave. The microwave requires 13.8 amps and the instructions require a dedicated 15 amp circuit. The problem is that the hood is wired on a local 15 amp lighting ciruit (5 bulb-50 watt and a 75 watt). What is involved in fishing a new 15 amp circuit ( should I run 20 amp?)

This may not be something I would want to undertake. Anybody any idea how much it would cost to have an electrician install the line?

Most microwaves are installed with a recpetacle up inside the cabinet above. Dedicated means just that, nothing else on the circuit. Fishing a new line back to the panel can run $200 and up but I have no idea where you are or the going rate. Does you panel have any open spaces for a new breaker?

The panel is in the basement, actually right below the range and there are available slots in the eletrical panel... St. Louis MO area

You may luck out with this placement but still be in the $200 ballpark