To remove it, take out the 4 bolts on the input shaft retainer and slide it off while holding the input shaft in place. Make a note to which side is up on the retainer. There are severl gooves on the inside for oil pasage. The wider groove goes on the bottom
There will be a few shims and a bearing race so put them aside. The shims go inside the retainer and then the race goes in.
The input shaft will be loose, but don't pull it out yet. What you want to do is tilt the trans forward so the input shaft is down. Rotate the shaft til the cutout is inline with the countergear and pull the shaft out. There are 15 roller bearings inside the snout and you don't want these to fall down inside the tranny otherwise you will need to pull the tailhousing and top plate off. Also make sure you don't drp the black 4th gear blocker ring inside.
With the input shaft out, take out the bearings and any thrust washers and set them aside.
To take the bearing off, you can either use a 3-jar puller or a press and pull it off. Then either use a press to push it or get a pipe that will fit on the bearing and bang it on that way. It's a bit more "redneck" but works if you have no access.
Reassembly is the opposite. To hold the bearings in place, pack them with petroleum jelly and set them in place. Install blocker ring and shims and put the input shaft back in. Then slide on the race and the front shims and bolt the retainer back up.
Sounds complex but it's easy to do.
What makes you think your input bearing went bad anyway??