As Burnham says Replacing the lnb is mostly likely your best bet but if you are changing dish this is a handy way of doing it.

Before you remove your old dish from the wall mount you could mark the center of the bracket on the mount. Setup your dish and lnb (elevation and skew) according to the instructions supplied with it, then when mounting, center the new bracket on the dish with mark on the wall mount. Although its not 100% accurate it is a simple way of doing it without the need for a meter.