How do you know if the shocks need replacing?

[fth]

How do you know if the shocks need replacing? We have a 2005 Classic 30. The previous owner welded on a 2" hitch receiver to the frame under the bumper for a bike rack. It has hit the ground so many times it has bent up the rear frame member making it almost impossible to open the drawer under the bumper. I want to remove it but it may be useful to use to bend the frame back down.