'86 Silverado...700R Trans whine/groan+rapid clicking

My 700R isn't workin' at-all right... Going into Drive, it hammers into gear, instead of the normal 2-stage/step engagement. It also makes a rapid clicking and moaning sound at idle, which decreases during load...
What should I be prepared to have replaced during rebuild? Thanks as usual, and ahead of time!
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ATF level, fluid quality? Last time the pan was dropped for a fluid and filter change?
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