I have replaced shocks myself a long long time ago, but I figure it can't be that hard. Off the top of our heads, we cannot remember if your car has struts or shocks. I'm wondering if the shock absorber went bad.
Bumps are ok, but when there's a small rise in the level of the road, the car goes up and down.
Specifically in the left front. It is possible that you do have a bad or broken shock. Also, check the shock mounts to see if they have been broken loose from the frame. Our 1995 Altima has 92000 miles on it. Looking forward to your response.