[xlr8or]

I would start with a new mechanic.

Sounds like he didn't get the distributor setup correct. You may also have a vacuum leak causing the high idle but that will usually show a lean condition not rich. There is nothing that could fry a timing light unless he plugged it in wrong.

Also verify that the plug wires are put back on correctly. Drivers side cylinders are front to rear 1,3,5,7 passenger side cylinders are front to rear 2,4,6,8 and the firing order is 18436572 going in a clockwise direction around the distributor cap.

Also verify the vacuum advance (if you have one) is plugged into "Timed vacuum" not manifold vacuum. For the timing on a 350 you should have 8 to 10 degrees BTDC initial timing with a total of 36 that should be all in by 2500 rpm.

Initial timing should be set with the vacuum advance disconnected and plugged with the idle at 1000 or less.

Hope this helps.