My '97 Buick LeSabre will not allow air flow through the dash vents. Heat and/or AC flows as directed to the floor and/or windhshield, but not through the dash vents. I’m told this might be due to a vacuum leak or a control switch in the climate control system. How expensive would it be to have this checked and repaired? Do I have to go to a Buick/GM dealer or can I find a certified shop through the mechanics page?
Take it to a reputable independent shop/tech (ask around for one).
Personally, I wouldn’t go to a dealer.
Shop rates vary around the country and this job is mostly labor.
You are likely right about what is wrong. Dealers are no better (or worse) than independent mechanics for almost anything you might need done on your car. They will almost always charge more per hour and often more for parts and supplies. They also tend to look at repairs a little different than the independent. A dealer may well recommend work that strictly may not be needed, but could be connected to the problem or maybe replace a part when a little repair would fix it ALMOST as good a new. There is no need to bring your car to the dealer for any service other than service that is going to be paid for by a recall or original warrantee. During the warranty period be sure to have all required (as listed in the owner's manual) maintenance done and to document all maintenance work. I suggest that most people would be better off finding a good independent (Not working for a chain) mechanic.
Note: Never ever use a quick oil change place. They are fast cheap and very very bad.