I had a tutorial somewhere, but here’s the basics: Choose your destination row and pick up all the stitches from that row (you can either use a smaller sized circ or even a piece of waste yarn - you can always switch to DPNs after cutting). Choose the row you will cut - probably a few rows into the rib to be removed, then you have a little room to play, plus it leaves you a tail to weave in later. Cut the ribbing off and unravel/pick the loose yarn pieces out til you are up to your destination row. Cut the old yarn off, but leave yourself a tail to weave in. Then, just add your new ribbing yarn and rib away! You will be knitting upside down from the original, but it’s really no different than doing a toe up sock, and I wouldn’t think upside down ribbing would be that noticeable.
ETA: Here’s the tutorial - it’s about a sweater, but same principle.
E(again!)TA: I think if you just googled “cut off ribbing and reknit” (no quotes), you’d get some more stuff to point you in the right direction. I don’t think it’s a technique that has an actual name.