shadesof gray
Did you disassemble the helical?
If it didn't start back on the same thread it probably won't focus correctly.
I just use a piece of ground glass held on the film rails & use a loupe to check focus.
Adjustment is usually readjusting the focusing scale once you have found infinity(3 screws on the distance scale).
If you're not getting infinity focus, you will have to unscrew the front assembly from the helical & restart it at another point. Remember, you have six or more start points on the helical threads. I would unscrew the assembly & advance one thread at a time 'til I hit inf. on the GG & then tighten everything down.