The mag tube is thin metal except at the very end where the barrel attaches. There it's thick for about 1/2". You want to use a strap wrench, or , as I did, wrap a piece of brass around it and grab it (carefully) with vice grips. Mine turned out very easily.
Remove the tubes, remove the follower and spring. Clean the interior of the mag tube, since you'll only get this chance every 30 years or so...
Insert the new spring and follower, put some low strength Loc-Tite on the threads, and reassemble.
This is a good technique to know, as mag tubes are easy to dent, and you should know how to replace one.