How do I Find a bad ground wire? Is it hard to trace? on 2000 Oldsmobile Silhouette

My turn lights go very fast when the brake is applied. Both turn lights are slightly lit when I engage the brake pedal without the turn signals on. I replaced three bad bulbs, but the problem wasn't solved. An employee of the auto store told me it was probably a rusted off ground wire. I was wondering if this is simple to resolve or if it would be inexpensive to have a mechanic fix.

Best thing to do is just let your mechanic take care of it! Save yourself time and money.