After selecting the vertex you want to move onto some other, press "v", to enable vert./CV snapping.
Then simply "drag&snap" the selected vert onto some other.
Finally, yes, re-select & merge verts.

ps: a much faster way to do that is to download and install the Bonus Tools. Inside this tools package, jut use the Poly Vertex Merge. Much faster. Click the vertexToMove, click the target. Done.