You have to take it apart. Even if the snap ring is still in one piece, I wouldn't take a chance on it by trying to use it again. Parts are worn or it wouldn't come apart. The groove in the syncro ring could also be worn. Use the good parts from the other trans.
Fred

1956 3100 Pickup/Red/350/3sp OD/PS/Disc Brakes
1957 Bel Air Sport Coupe/Red/355/TH350/PS/Disc Brakes
2017 Silverado LT Single Cab SB/Black/5.3/6 Speed Trans
1947 Willys CJ2A w/F-Head engine