She says smoke comes from steering wheel and since there are no other electronics except the horn or air-bag in the wheel, any suggestions other then a mechanic at 90 bucks an hour. Or could engine smoke come up the steering column?

Then it should not take a mechanic an hour to figure out what is wrong. They have electronic sensors that will tell them if it is exhaust gases.
BTW Mechanics do not get that kind of money..the place of business is charging that(if it is a dealership), However, as this sounds like a fault l would take it to Pontiac dealer with a safety complaint(recall or something) Does not matter it is 2003. What if u were cruising down the hiway at 70MPH & the airbag blows? You r gonna kill others. Lawsuits will plague GMC. Let them fix it. It should come under lifetime warranty.

l had a van that would smell like smoke when leaves got down under the hood, onto the hot engine. Could that be the problem?

l know what it is, to end the speculation.

The ignition switch itself is frying. It is to the left side of the column, or in that are. It is NOT the key cylinder, but a separate electrical part actuated by the key through a rod or lever, and they burn up all the time.

It is on slow blow right now. soon the car will quit and stall. where? In the middle of the freeway.

l used to have a car that did that. The truth is, there are myraid sets of contacts in the turn signal switch, and the horn brushes, and the horn contactor, and the ignition switch as Doc mentioned. A bunch of 'em. Dozens And apparently there is some pair of contacts in there that had some resistance it was not supposed to and got hot.

l ignored it. It smoked for years.

It is more than likely that she is experiencing an ignition switch problem. It is a common problem on these cars.