1976 Chevy Stock 4x4 Question

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I'm brand new to 4wheel drive. I just bought my grandfathers 76 4x4 after his passing. Besides fixing safety issues and tackeling leaks here and there I'm going to replace/repair/relube all the ujoints and differentials. I've done the rear with all new seals and oil, the bearing and such are good to go. Next is the front diff.

My questions are these. What is the best/correct way to engage 4wd high and low with the manual hubs? How I have been told is to get out and lock the hubs, then just start driving and push in the clutch, slide the 4wd lever to 4h, let the clutch back out and continue driving and ****ing as normal. I've got the M20 4spd by the way. After reading the pickups owner's manual I'm kind of under the impression that I don't even have to use the clutch to engage 4H from 2H. Is that correct?

And what about disengaging 4wd? After a drive to my girls farm in Jersey the pickup was warm and wend into 4wd easily and made no excessive noise. And I know it was engaged because on tight turns I could feel the wheels "skipping" over the dirt from the differential being locked. But the next morning it was about 7 degree's out and there was a godawful noise coming from the transfer case as I backed up and as I drove forward. It also made a hell of a rattling racket when just left to idle. After getting it in 2H and driving for a few minutes it seemed like the gears fully disengaged and everything was normal.

I've pretty much resigned to the fact that I'll have to rebuild the transfer case at some point. I just want to make sure I don't hasten that event.