Chris,
The Singer 457s are easy to fix. The only thing to watch out for is the nylon thrust washer on the left end of the main shaft. If it's bad you can replace it with the snap in one. But you might have to adjust the metal bushing that controls the end shake of the main shaft. You have to crank the set screws down TIGHT or they will vibrate loose the first time you do a ZZ with it.
I just did one earlier this week.
Joe