The Kodak Viewfinder/Rangefinder mechanism has 7 adjustments; doing it without the manual is a pain. teh repair manual is available on EBay. If you can use jewlers screwdrivers and are comfortable opening up a camera, the Retina's are not too bad.
Some of the adjustments require taking the RF/VF out of the camera, done with two (or three) screws. I have done this on two cameras, a IIIS and an Auto III with the same style finder.
If you want to try it yourself, feel free to PM me. If you do not mind having the pro's do it, it is well worth the money.