how much to repair the a frame on a 2005 buick lacrosse

This car has no frame. If the body is bent it could be totaled. Only a body shop could give you an estimate.

Try a collision center or some place with a frame jig, they can advise on repairing or replacing sub frame. If it's a bent control arm, you *might* be able to repair it, or it might be better to replace the entire subframe. You can buy new replacement frames for less that $400, even as low as $150 to 200 used. Swapping it in is another matter, as engine & trans has to be suspended, suspension removed, brakes hung off to side, then subframe dropped from beneath car and installed from below. It's a lot of work, and prices are going to be all over the map as it's not something most shops get involved with.