I've removed the agitator assy to try and get to the spin bearing. I removed the four screws in the tub, but it won't pull out. Does it thread onto the main spindle, or shoul I be able to pull it free?

This is wrong information, you have to remove the outer tub, tranny stays in place!
First, verify bad spin bearing. Lift up the top, turn the washer to spin and hold the spin basket from turning, if now no spin bearing noises, this verifies a bad spin bearing, if noise continues, you have a bad tranny.
Got to web site www.applianceaid.com and check out the Atlantis washer bearing replacement article. To fix, you will need the special spanner wrench. To spread the tub springs before tub removal, you can spread the springs with electrical outlet boxes, no need for the spring stretcher tool! You can also download the Atlantis repair manual at web site www.appliancejunk.com, but this article is complete.
This is a rather extensive repair, probably a 3 hr job, good luck, please post results.

i replaced the bearing, i made a web site w/pics on how to do it, check it out here
https://sites.google.com...air/maytag-washer-repair
[URL="http://www.geocities.com/maytagrepairwasher/"][/URL]