The only way I have repaired the neptunes with bad tub bearings is to install the outer tub assembly.
Outer tub assy kit, Includes ball bearing, rear bearing, water deflector, hose clamp, spacer, motor isolator, plug & Lip Seal
Your looking around $200 for that part.
If you scroll down the site here and look on the left hand side you will see a box that you can enter your neptune model number in.
This will give you all the parts diagrams and prices.
The bearing is factory installed and not sold as a Maytag part.