On my Meltrail trailer with surge brakes there is a refill cap for DOT 3 on the top.under the spot where the hitch goes to the ball there is what appears to be a "shock absorber"about 9 inches in length.I notice this year the the hitch moving forward and backward quite easily while on the truck as though the shock has lost it's hydralics and become weak>Is this a case of just replacing the shock,how easy is it,and is it unsafe to use the way it is now?Thanks