Steering Wheel problems of the 1998 Buick Riviera

Steering wheel has developed a very significant "wobble" which exists regardless of what tilt position it is in. The wobble is diagonal, from northeast to southwest in direction, and the apparent pivot point of the wobble is just behind instrument panel level. Had car at dealer for other work, and they commented on it too. Did not call it a safety issue though. . . Wanted $120 to fix it. I declined at the time, since they didn't think there was a safety concern. I would tend to differ with their opinion though, and feel they should repair this at no charge due to it being the steering mechanism involved. I've heard this complaint from many other 95-99 Riviera owners, and it seems to be epidemic among these cars.