There should be no need to realign the dish unless the extreme areas of the tracking arc are out
You should first check there is enough room behind the dish to install the new actuator (It will be up to six inches further back, which may hit a wall/chimney)
Then will the dish be able to move the further distances East or West ? Not just the limits of the reflector (again it might hit other objects) but the bearings in the polarmount - Lenson Heath dishes for example are limited to 45 degrees either side of South
Replacing the actuator for one of the same shaft diameter is straightforward, if the original joint on the back part of the dish is uncorroded then reuse it
Set the mechanical limits up correctly when its all done, the receiver should be able to reset ther electronic limits without difficulty
Ive got nothing surrounding the dish, so it will move further (its on a flat roof). The arm that is joined onto the back of the dish is a little corroded (the dish has been there since early 90s!). But i thinks its okay to re-use.
Do u recommend the Jaeger 18" acutuator, or are there any that are supposed to be quicker / more silent?
what a mash up! - tried to install my 18! jaeger actuator in a hurry - blagged it - went to the receiver upstairs to move my dish (and set limits to test), went back on the roof and the actuator had twisted and snapped itself!
Im getting another actuator and getting a professional to do it next time!