Replacing the feed horn

[lme]

I'm replacing the c/ku Chaparral corotor II feed horn with a new genuine one. Noticed that the scalar ring in wider/thicker then the 8 years old one from TEK2000 store, witch I believe was a used one to begin with (see screw marks):
[Only registered and activated users can see links. ]
My question is if there is any procedure &/or tools, to install the new scalar ring parallel and centered to the face of the dish.
I'm thinking about a laser pointer (beam) !!
Forgot to mention that last month we had 2 tornados in the area; 1 small branch slightly bent 2 holding arms and knocked
off the feed horn assembly: cone cover on the ground, so I assume that the hole assembly is out of the alignment. The signal is a bit less then before. I also had to replace the servo.
Any input is welcome.Thx.