I'll add my ha' penny's worth. Have it done by a specialist. I would suggest you have a very solid idea of how much less choke you want. You will have more success if you keep in mind the 28 ga "limitations" of a smaller pattern circle, say 24" at about 30 yards instead of the traditional 30" at 40 yds.
I love the 28, been shootin' one for upland for 'bout twenty years. Taken pheasants, woodcock, qual and grouse. Plumb deadly on rabbits. Choked Mod and Full. Will knock a rising pheasant sideways. Some like the first barrel opened up more to IC. That's fine just make sure your pattern is dense.
Other's mileage may vary.
