I would suggest sterling silver instead of nickel. Nickel silver is just tacky, and whoever does the engraving will thank you. The screws in epoxy is good. Shape the inlay, set it in place with superglue in a couple of spots away from the edges. Use very small drops. Then do a careful scribe around the inlay. Remove it and cut out the wood inside the scribe. Get the inlay set in the cutout so that a few thousanths are proud above level, then epoxy in place. When the epoxy is dry file down to the wood, then sand and polish. If you confine the epoxy to where it does not squeeze out of the edges, and you end up with small gaps, the silver can be carefully hammered to fill. Another plus for real silver. You will have to refinish the area around this, If you want a very good job of the inletting.